Why Did This Expedition Happen?
The Lewis and Clark Expedition did not begin with a map or a boat. It began with an obsession. Thomas Jefferson had dreamed of a transcontinental American expedition for nearly two decades before he had the political authority and geographic justification to launch one. Understanding why the expedition happened requires understanding three overlapping forces: Jefferson's lifelong fascination with the West, the sudden availability of the Louisiana Territory, and the fierce competition among European powers for control of North America's Pacific Coast.
Jefferson believed, as many of his era did, in the existence of a "Northwest Passage," a practical water route connecting the Missouri River system to the Pacific Ocean through the Rocky Mountains. Such a route would give American merchants direct access to the lucrative China trade without having to sail around South America or Africa. He was wrong about the Northwest Passage (no such practical water route exists through the Rockies), but the search for it drove the expedition westward with genuine urgency.
Jefferson was also a scientist. He was President of the American Philosophical Society, the leading scientific organization in the United States, and he had a voracious appetite for natural knowledge. The West was, from a scientific standpoint, entirely unknown. What animals lived there? What plants? What Native nations? What were the soils like, the climate, the mineral resources? Jefferson wanted to know everything.
The Louisiana Purchase, The Trigger
Jefferson had been quietly planning a western expedition for years, but two political obstacles stood in his way: the territory was owned by France and Spain, and Congress would never fund an expedition into foreign sovereign land. Both obstacles dissolved in a single transaction in April 1803.
Napoleon Bonaparte had acquired Louisiana from Spain in 1800 with the intention of building a French empire in the Western Hemisphere, anchored by the sugar colonies of Saint-Domingue (modern Haiti). The Haitian Revolution, led by Toussaint Louverture and later Jean-Jacques Dessalines, destroyed that plan. By 1803, with French forces devastated by yellow fever and guerrilla warfare in Haiti, Napoleon abandoned his American ambitions. He needed money for the coming war with Britain. He offered Jefferson the entire Louisiana Territory, 828,000 square miles, for $15 million.
Jefferson had doubts about the constitutional authority to purchase foreign territory, but he set them aside. The purchase was too important to refuse. On April 30, 1803, the deal was signed in Paris. The United States doubled in size overnight. And now the land west of the Mississippi, including the Missouri River, which Lewis and Clark were already preparing to explore, was American territory.
The Mission, What Jefferson Actually Wanted
Jefferson's formal instructions to Lewis, sent June 20, 1803, laid out five primary objectives in order of priority:
Find the Northwest Passage
The object of your mission is to explore the Missouri River, and such principal stream of it as, by its course and communication with the waters of the Pacific Ocean, may offer the most direct and practicable water communication across this continent, for the purposes of commerce.
Establish Diplomatic Relations with Native Nations
Make the Native nations acquainted with the peaceful and commercial aims of the United States. Establish peaceful relations. Assess the state of inter-tribal politics. Identify which nations were most strategically important for American trade.
Conduct a Scientific Survey
Observe and document soil, climate, flora, fauna, minerals, and any evidence of prehistoric animals. Collect specimens. Take astronomical observations at key geographic points to establish latitude and longitude.
Assess Commercial Potential
Evaluate the fur trade potential of the region. Identify what goods Native nations would want in exchange for furs. Assess whether American commercial interests could compete with the British fur trade already operating on the upper Missouri.
Document Everything
Keep detailed daily journals. Record everything. Map everything. Send regular dispatches downstream whenever possible. The records of this expedition are as important as the expedition itself.
Commissioning the Expedition
In January 1803, before the Louisiana Purchase was even completed, Jefferson sent a secret message to Congress requesting a $2,500 appropriation for a "literary expedition," the word "literary" being a diplomatic euphemism for scientific, designed to obscure the politically sensitive nature of sending American soldiers into French and Spanish territory. Congress approved the funding on February 28, 1803.
Jefferson had already selected his commander: Meriwether Lewis, his personal secretary and a capable army officer who had grown up near Jefferson's Monticello in Virginia. Lewis spent the spring of 1803 in Philadelphia studying botany, zoology, celestial navigation, and medicine with some of the leading scientists in the country. Jefferson personally tutored him in the natural history observations he would be expected to make.
Lewis then invited William Clark to share command. Clark had been Lewis's commanding officer in the army years earlier, and Lewis trusted him completely. Clark accepted by letter in July 1803, writing that "no man lives with whom I would prefer to undertake such a trip." Jefferson gave Lewis the rank of captain; the War Department, in a bureaucratic slight that rankled throughout the expedition, gave Clark only a lieutenant's commission. Lewis refused to acknowledge the difference, he addressed Clark as "Captain Clark" for the entire journey, and the men under their command were never told otherwise.
The Key Figures of the Corps of Discovery
The Corps of Discovery was 33 permanent members plus several temporary additions. Most were young army enlisted men, recruited for physical strength, frontier skills, and willingness to face the unknown. But four figures shaped the expedition's history more than any others.
- Born August 18, 1774, in Albemarle County, Virginia, neighbor to Thomas Jefferson
- Served as Jefferson's private secretary from 1801 to 1803, giving him unique access to the president's vision for the West
- Had no formal scientific training but taught himself botany, zoology, and celestial navigation in preparation for the expedition
- Described over 170 plants and 120 animals previously unknown to science
- Suffered from severe depression throughout his life, Jefferson was aware of this when he appointed him
- Died on October 11, 1809, at Grinder's Stand on the Natchez Trace in Tennessee, under circumstances that remain disputed, most historians conclude it was suicide, though some argue murder
- Was 29 years old when the expedition departed and 35 when he died, he never published the journals
- Born August 1, 1770, in Caroline County, Virginia, the younger brother of Revolutionary War hero George Rogers Clark
- Had extensive frontier military experience before the expedition, including service in campaigns against Native nations in the Ohio Valley
- Was a gifted cartographer, his maps of the West remained the most accurate available for decades after the expedition returned
- Brought his enslaved servant York on the expedition, York's presence fascinated many Native nations who had never seen a Black man
- York was a significant asset to the expedition, impressing Native peoples with his strength and appearance, but Clark refused to free him after the expedition despite York's requests
- After the expedition, Clark served as Indian Agent for the Louisiana Territory and later as Governor of Missouri Territory
- Lived to 68, the longest-lived leader of the Corps, and saw the West transformed by the very routes he mapped
- Born around 1788 into the Agaidika (Salmon Eater) band of the Lemhi Shoshone in present-day Idaho
- Kidnapped as a child, around age 12, by a Hidatsa raiding party and taken to the Mandan-Hidatsa villages in North Dakota
- Was purchased or won in a gambling game by French-Canadian trader Toussaint Charbonneau, who made her one of his wives
- Was approximately 16 and pregnant when Lewis and Clark hired Charbonneau at Fort Mandan, she gave birth to son Jean-Baptiste on February 11, 1805
- Carried her infant son, nicknamed Pompey by Clark, on her back for the entire westward journey
- Recognized her brother Cameahwait as the Shoshone chief who held the horses the Corps desperately needed, her presence enabled the critical horse negotiation
- Served not only as interpreter but as a living signal of peaceful intent, her presence with an infant told every nation they encountered that this was not a war party
- Had her preference written down by Clark in the poll at Station Camp in November 1805, when the Corps chose where to spend the winter
- The date of her death is disputed: some records indicate she died in 1812 at Fort Manuel in present-day South Dakota; other records suggest she lived until 1884 on the Wind River Reservation in Wyoming
- Had dreamed of exploring the West for nearly 20 years before the Louisiana Purchase made the expedition politically viable
- Personally selected Meriwether Lewis for the command, knowing Lewis from his time as presidential secretary
- Wrote the detailed instructions that governed every aspect of what Lewis and Clark were to observe, record, and accomplish
- Negotiated the Louisiana Purchase in 1803 for approximately 3 cents per acre, doubling the size of the United States
- Was a trained scientist and naturalist himself, the specimens the Corps sent back were of genuine scientific interest to him
- Had Congress fund the expedition with a $2,500 appropriation, the final cost was approximately $38,000, still considered one of the best returns on investment in American history
- Received the first dispatch from the Corps in 1805 when the keelboat returned to St. Louis, he was thrilled with the specimens and maps
- Never saw the West himself, he died on July 4, 1826, the 50th anniversary of the Declaration of Independence
The Rest of the Corps
The other members of the permanent Corps were chosen for specific skills: the ability to hunt, to handle boats, to interpret, to make tools, and to survive. Several speak to the remarkable human range of the expedition:
York
William Clark's enslaved servant, the only Black member of the Corps. York's presence astonished every Native nation they encountered, many had never seen a Black person. He participated fully in the expedition's labor and in the vote at Station Camp in November 1805. Clark refused to free him after the expedition despite repeated requests.
Sgt. John Ordway
The most reliable and steady of the sergeants. Ordway's journal is one of the most detailed enlisted accounts of the expedition and provides crucial corroboration for the captains' journals. He kept a record of accounts and provisions throughout the journey.
Sgt. Patrick Gass
The expedition's carpenter and the author of the first published account of the journey (1807). Gass lived to be 98 (1771-1870), the longest-lived member of the Corps. He tried to enlist in the Union Army during the Civil War at about age 90 before being talked out of it.
George Drouillard
Half-French, half-Shawnee, Drouillard was the expedition's most skilled hunter and its primary sign-language interpreter with Native nations. Lewis considered him indispensable. He could communicate with nations whose spoken language no one in the Corps knew through an inter-tribal sign language used across the plains.
Pvt. John Colter
On the way home in August 1806, Colter asked for his discharge at the Mandan villages and went back west with two trappers, becoming one of the first American Mountain Men. He explored the Yellowstone region around 1807-1808, becoming the first American citizen to see what would become Yellowstone National Park. His reports of thermal features were so implausible that contemporaries mocked them; the nickname 'Colter's Hell' first referred to a thermal area near present-day Cody, Wyoming, and was later applied to Yellowstone's geysers.
Toussaint Charbonneau
Sacagawea's husband, hired at Fort Mandan as a French interpreter. Charbonneau was, by most accounts, not a particularly skilled frontiersman and at least once panicked at the helm of a pirogue during a windstorm, requiring Sacagawea to calmly retrieve essential documents and instruments from the swamping boat.
The Journey West, Step by Step
From Camp Dubois in Illinois to Fort Clatsop on the Oregon coast, the Corps traveled approximately 4,000 miles west over 18 months. Every entry below is a real event documented in the expedition journals. Nothing was easy.
Journey Timeline
Lewis and Clark established their winter camp at the mouth of the Wood River in Illinois, directly across from the confluence of the Missouri and Mississippi Rivers. For four months the captains drilled their men, tested equipment, gathered intelligence from fur traders and Native American informants, and organized the enormous quantity of supplies Jefferson had authorized.
The men practiced firing their weapons, learned celestial navigation, and were evaluated constantly. Those who proved unfit were discharged. By spring, the Corps of Discovery numbered 33 permanent members plus a small contingent of soldiers detailed to accompany them only as far as the first Mandan village.
The camp sat on the Illinois side because Spain, which still administered Louisiana until the formal handover, would not allow an armed American party to winter on the west bank. The transfer of Upper Louisiana to the United States was carried out at St. Louis on March 9 and 10, 1804, an event some of the men witnessed.
The winter was also spent refitting the 55-foot keelboat with storage lockers and a collapsible mast, and copying the maps and river notes that St. Louis traders such as James Mackay had compiled from earlier trips up the Missouri.
The Corps of Discovery set out from Camp Dubois on May 14, 1804, with Lewis remaining briefly in St. Louis to finish paperwork while Clark led the men up the Missouri River. Lewis joined the party a few days later at St. Charles.
The primary vessel was a 55-foot keelboat capable of carrying ten tons of cargo, accompanied by two smaller boats called pirogues, one painted red and one white. Counting the temporary soldiers and hired boatmen who would turn back at the Mandan villages, roughly 45 people started upriver.
The Missouri was brutal from the first mile: swift, shallow in places, its banks caving into the current and its channel blocked by submerged trees that could hole a hull. The men poled, rowed, hauled the boats by rope from shore, and sailed, making perhaps 10 to 15 miles on a good day.
Discipline problems surfaced early. Courts-martial in the first weeks punished men for being drunk on guard duty and for stealing whiskey; one private, John Newman, was later expelled from the permanent party for 'mutinous expression' and sent back from Fort Mandan.
At what Lewis and Clark named Council Bluffs, near present-day Fort Calhoun, Nebraska, the captains held their first formal council with Native leaders on August 3, 1804, in this case representatives of the Oto and Missouri nations. It was the first of many such councils.
Jefferson's later letter of January 22, 1804, written after the purchase, had been explicit: tell every nation you meet that their former French and Spanish trading partners had given up the land to the United States, and that they now had a new father in Washington who wished to trade with them and keep peace among them.
Lewis and Clark distributed peace medals bearing Jefferson's likeness, American flags, military coats, and trade goods, and Lewis delivered a lengthy set speech translated through a chain of interpreters. The councils were not always successful; some nations were deeply skeptical of American claims and more interested in the immediate gifts.
The larger diplomatic goal, pulling the fur trade away from British traders on the northern plains and toward American merchants at St. Louis, mostly failed. British companies kept their hold on the northern trade for another decade, and several nations the Corps met, including the Blackfeet, stayed hostile to American traders for years.
Sergeant Charles Floyd died near present-day Sioux City, Iowa, on August 20, 1804, becoming the only member of the Corps of Discovery to die during the expedition. He was 22.
His symptoms, severe abdominal pain, vomiting, and rapid collapse, are consistent with a ruptured appendix, a condition uniformly fatal in 1804 regardless of the care available. Clark wrote that Floyd died 'with a great deal of composure,' saying, 'I am going away. I want you to write me a letter.'
The men buried him with military honors on a bluff overlooking the river and named it Floyd's Bluff. Patrick Gass was then elected by the men to replace him as sergeant, the only time a Corps vacancy was filled by a vote.
That the expedition lost only one man across roughly 8,000 miles and 28 months, and that one to an illness no physician of the era could treat, is often cited as extraordinary for the time. The stone obelisk marking Floyd's grave, dedicated in 1901, was later named the first National Historic Landmark in the United States.
The most dangerous moment of the first year came at the Bad River confluence near present-day Pierre, South Dakota, on September 25, 1804, when the Teton Sioux (Lakota) tried to seize one of the pirogues as a toll for passing through their territory.
The Teton controlled the upper Missouri and had extracted tribute from traders for years. When warriors grabbed the boat's towrope and refused to let go, Clark drew his sword and Lewis had the keelboat's swivel cannon and blunderbusses trained on the men on shore. Several hundred armed warriors faced roughly thirty members of the Corps, and for the better part of an hour a fight seemed certain.
A chief the captains called Black Buffalo finally ordered the rope released, and both sides drew back. The standoff flared again over the next two days before the Corps moved on, badly shaken; Clark called the Teton 'the pirates of the Missouri.'
The encounter had a long tail. Jefferson, reading Clark's report, singled out the Teton Sioux as a nation that had to be brought to heel, and U.S.-Lakota relations stayed tense for decades, culminating in the wars of the 1860s and 1870s. On the return trip in 1806 the Corps passed the same villages without stopping.
In late October 1804 the Corps reached the Mandan and Hidatsa villages near present-day Bismarck, North Dakota, the largest permanent Native settlement on the upper Missouri, home to roughly 4,000 to 4,500 people, more than lived in St. Louis or in Washington at the time.
The captains had been told these earth-lodge towns were the crossroads of the northern plains trade. The men built Fort Mandan, a triangular log stockade about 60 feet on a side, and settled in for a winter that reached forty below zero; several suffered frostbite bad enough to cost them toes.
It was here the expedition made its most important addition: it hired the French-Canadian trader Toussaint Charbonneau as an interpreter, and with him came his teenage Shoshone wife, Sacagawea, then pregnant. She gave birth to a son, Jean-Baptiste, at the fort on February 11, 1805.
The winter was spent hunting with Mandan companions, repairing gear, and interviewing Hidatsa men who had raided far to the west, whose descriptions of the Missouri's falls and the mountains beyond shaped the planned route. British traders from the North West Company visited the fort, and relations were correct but wary.
On April 7, 1805, Lewis and Clark sent the large keelboat back downstream to St. Louis, crewed by about a dozen men, loaded with everything gathered so far: pressed plants, animal hides and skeletons, mineral samples, Mandan artifacts, the captains' journals and maps to date, and cages holding four live magpies, a prairie dog, and a sharp-tailed grouse.
The shipment reached Jefferson that autumn; the prairie dog and one magpie arrived alive, and Jefferson sent much of the collection on to the American Philosophical Society in Philadelphia and to Charles Willson Peale's museum.
Sending the keelboat back committed the Corps fully to the unknown. Going forward, the party of 33, the two captains, York, Sacagawea and her infant, Charbonneau, and the enlisted men, had only the two pirogues and six dugout canoes.
Lewis wrote that evening that his little fleet, 'not quite so respectable as those of Columbus or Capt. Cook,' still carried men 'in excellent health and sperits,' and that he esteemed the moment of departure 'among the most happy of my life.'
In early June 1805 the Corps reached a major river fork that appeared on no map and that no Hidatsa informant had mentioned. The two branches were nearly equal in size.
Every enlisted man believed the north fork was the true Missouri; it was wide and muddy like the river they knew. Lewis and Clark judged that the clear, swift, gravel-bottomed south fork must rise in the mountains and was therefore the Missouri. They spent about a week scouting both, each captain leading a party up one branch.
Lewis pressed up the south fork and, on June 13, heard the roar of falling water, the Great Falls, confirming the choice. Had the Corps taken the north fork, the Marias River, they would have traveled hundreds of miles the wrong way and almost certainly failed to cross the mountains before winter.
The men's willingness to follow the captains' judgment against their own is often cited as a measure of the Corps' discipline. Lewis named the north fork the Marias River, after a cousin, Maria Wood, noting drily that 'the hue of the waters of this turbulent and troubled stream' did not suit 'that lovely fair one.'
Lewis, walking ahead of the boats, became the first American citizen to see the Great Falls of the Missouri, in present-day Montana, on June 13, 1805. He called it 'the grandest sight I ever beheld,' then fretted that he lacked the pen of a great landscape painter or poet to do it justice.
The elation faded fast. From Hidatsa accounts the captains had expected a single cascade they could portage in half a day; instead they found five falls strung over about 18 miles. The portage took roughly a month.
The men cut wagon wheels from a single large cottonwood, built crude carriages, and dragged the canoes and tons of baggage overland in furnace heat, across ground carpeted with prickly-pear spines that pierced their moccasins, tormented by mosquitoes and gnats. Hailstorms knocked men flat, and a flash flood in a ravine nearly killed Clark, Sacagawea, and her baby.
Lewis's prefabricated iron-frame boat, the 'Experiment,' was assembled here and covered with sewn hides, but with no pine pitch to seal the seams it leaked hopelessly and had to be abandoned, forcing the men to hollow out two more dugout canoes.
By mid-August 1805 the Corps had climbed into the Rocky Mountains and urgently needed horses to cross the Continental Divide. Horses meant finding the Shoshone, Sacagawea's people.
Lewis, scouting ahead with three men, crossed Lemhi Pass on August 12, becoming the first U.S. citizen to stand on the divide. Descending the far side he saw a westward-flowing stream, the first hard evidence that the easy all-water route to the Pacific that Jefferson hoped for did not exist.
Lewis reached a Shoshone band led by a chief named Cameahwait and, after tense first contact, persuaded them to come meet the main party. When Clark arrived with Sacagawea, she began to weep and press her fingers to her mouth, the Shoshone sign of kinship: Cameahwait was her brother, and she had been seized from this very country as a girl.
The reunion, and days of hard bargaining, secured about 29 horses and mules and an elderly guide the men called Old Toby. The Shoshone themselves were close to starving, driven into the mountains by better-armed Plains enemies, and parted with the animals reluctantly.
September 1805 brought the hardest weeks of the journey: crossing the Bitterroot Mountains by the Lolo Trail, in present-day Idaho and Montana.
A guide had warned the captains the route was severe, and if anything he undersold it. The trail ran through fallen-timber forest, over bare 7,000-foot ridges, through snow falling in early September. Horses slipped on ice and rolled down slopes, one carrying Clark's writing desk, which was smashed.
Food gave out within days. The men killed and ate three of their colts, then boiled portable soup, candles, and bear's grease, and nearly everyone fell ill from the change of diet. Clark wrote that he had never been as wet and hungry in his life.
On September 20, Clark's advance party stumbled out of the mountains onto the Weippe Prairie, where a Nez Perce woman named Watkuweis, once rescued from captivity by white traders, argued for helping the starving strangers rather than killing them. The Nez Perce fed the Corps camas root and dried salmon, agreed to keep its horses over the winter, and showed the men how to burn out dugout canoes for the run to the Pacific.
On October 16, 1805, the Corps reached the junction of the Snake and Columbia Rivers near present-day Pasco, Washington, guided there by two Nez Perce chiefs, Twisted Hair and Tetoharsky.
The Columbia was nothing like the Missouri, fast, cold, salmon-choked, cutting through walls of dark basalt. Between the Snake confluence and tidewater it dropped hundreds of feet through rapids and two great obstacles, Celilo Falls and the narrows at The Dalles, where the whole river squeezed through channels only tens of yards wide.
Short of time and food, the Corps ran most of the rapids rather than portage, sending the non-swimmers and the journals around by land. Crowds of Chinookan people lined the cliffs expecting to see the canoes wrecked; the crews got through, which raised their standing with the river nations.
The dense, powerful villages of the Columbia lived on dried and pounded salmon traded up and down the coast, and the captains recorded the first detailed American account of the Northwest trade, including European goods, muskets, cloth, a sailor's jacket, that had reached the river from ships years before the Corps arrived.
On November 7, 1805, Clark wrote, 'Ocian in view! O! the joy,' though what he actually saw was the broad, storm-whipped estuary of the Columbia, not the open Pacific. The Corps was then pinned on the north bank for weeks by gales and high water, in a spot the men called 'dismal nitch.'
They had come roughly 4,000 miles from Camp Dubois. Once the weather eased, small parties reached the real coast; Clark carved 'William Clark December 3rd 1805. By Land from the U. States' into a tree near the shore.
On November 24, facing a choice of where to winter, the captains put it to a vote of the whole party, and the tally recorded York, an enslaved man, and Sacagawea, a Native woman, each giving an opinion, 65 years before the 15th Amendment barred racial discrimination in voting and 115 before women could. The majority favored the south bank, where elk were reported and salt could be boiled from seawater.
They built Fort Clatsop on the Netul River near present-day Astoria, Oregon, and moved in on Christmas Day 1805.
Fort Clatsop was named for the Clatsop people, a Chinookan nation whose villages lay nearby and who visited often to trade fish, roots, and dogs, which the men had learned to eat and mostly preferred to lean elk.
The winter was punishing: of 106 days there, only about 12 were free of rain or fog. Clothing rotted, fleas infested the bedding, and elk grew scarce enough that the men sometimes ate spoiled meat. A detail kept a fire going day and night at a salt-making camp down the coast at present-day Seaside.
Lewis used the months to write long natural-history entries on the plants, animals, and peoples encountered, while Clark completed a master map of the route from Fort Mandan to the Pacific, the first reasonably accurate map of the American Northwest.
The captains also left, posted inside the fort and handed to local chiefs, a note asking any ship's captain who found it to forward word of the expedition's success to the United States, in case the party did not survive the return. A copy did eventually reach the East Coast by sea, carried by a trading ship by way of Canton, after the Corps was already home.
Fort Clatsop, Journey's End and the Return
Fort Clatsop was a small, damp, flea-infested wooden fort on the Netul (now Lewis and Clark) River, a few miles south of the Columbia, near present-day Astoria, Oregon. The Corps built it in December 1805 and occupied it until March 23, 1806. It was named for the Clatsop people, the local Chinook-speaking nation.
The winter was dominated by misery and work. It rained or was foggy on 94 of the 106 days. Fleas were a constant torment, Lewis wrote that it was impossible to rid clothing of them. Elk, the Corps' primary food source, became so scarce that hunting parties regularly returned empty-handed. Several men developed venereal disease from contact with coastal Native women.
Despite the conditions, Lewis used the winter productively. He wrote detailed natural history notes on hundreds of species, refined his astronomical observations, and prepared extensive descriptions of the Native peoples of the Pacific Northwest. Clark worked on his maps, refining the cartographic record of the entire route from the Mississippi to the Pacific.
On March 23, 1806, the Corps abandoned Fort Clatsop and began the return journey. They left behind a list of the expedition's members and a summary of their route for any ship that might find it, in case they did not survive the return. They arrived back in St. Louis on September 23, 1806, after 28 months in the wilderness. The city celebrated for days. Most of America had assumed they were dead.
The Moments That Made the Expedition
Half a dozen moments during the Lewis and Clark Expedition could have ended it. The wrong decision at any of these junctures, or the absence of one particular person, and the Corps of Discovery would have become a footnote rather than a founding story.
Napoleon Bonaparte had re-acquired Louisiana from Spain in 1800 with grand plans for a French empire in the Western Hemisphere. Those plans collapsed when the Haitian Revolution succeeded in 1803, eliminating France's most valuable Caribbean colony and making a North American empire strategically useless.
Napoleon offered the entire Louisiana Territory, about 828,000 square miles, to the United States for $15 million. Jefferson had sent James Monroe to Paris to help buy only New Orleans and West Florida; on April 11, 1803, a day before Monroe arrived, the French offered the American minister Robert Livingston the whole territory. The deal was completed on April 30, 1803.
Jefferson was privately uncertain whether he had the constitutional authority to make the purchase, since the Constitution did not explicitly permit the federal government to acquire foreign territory. He set the question aside, and the acquisition doubled the size of the United States.
The purchase reshaped American politics. New England Federalists denounced it as unconstitutional and warned it would pull power westward, and some of their leaders talked openly of secession. The Senate ratified the treaty 24 to 7 in October 1803, and the United States formally took possession of Upper Louisiana at St. Louis in March 1804, weeks before the Corps set out.
On June 20, 1803, Jefferson sent Lewis his formal instructions for the expedition. Lewis was to find a practical water route across the continent to the Pacific and to study every Native nation he met, its language, customs, trade, diseases, and relations with its neighbors.
He was to catalog every plant and animal, collect specimens, take climate measurements, and map everything, fixing the latitude and longitude of significant features. He was to assess the soil, timber, minerals, and commercial possibilities of the country.
He was also to treat the Native nations 'in the most friendly & conciliatory manner which their own conduct will admit.' Jefferson was, in a single expedition, sending a scientist, a diplomat, a military officer, and a mapmaker.
Jefferson had the letter reviewed by his cabinet and arranged for Lewis to be tutored in Philadelphia by the physician Benjamin Rush, the botanist Benjamin Smith Barton, the astronomer Andrew Ellicott, and the anatomist Caspar Wistar. The instructions even told Lewis to make 'several copies' of his notes against loss and to send them back whenever he could.
By August 1805 the Corps faced an existential crisis. They had reached the Continental Divide but had no horses to cross it, and without horses the expedition would fail.
The only nation in the area with horses was the Shoshone, and their chief, Cameahwait, was deeply suspicious of the strangers. The breakthrough came when Sacagawea arrived with Clark's party: she recognized Cameahwait as her brother, and the emotional reunion transformed the talks.
Cameahwait provided horses and an elderly guide the men called Old Toby for the mountain crossing. Without this exact chain of circumstances, Sacagawea's kidnapping years earlier, her survival, her presence with the Corps, and the coincidence of her brother leading this particular band, the expedition almost certainly could not have crossed the Rockies.
Cameahwait, hungry and eager to take his people east to hunt buffalo, twice nearly left before the trades were finished, and Lewis had to shame and coax him into staying. The Corps bought roughly 29 animals, largely with uniform coats, knives, and other goods, including Clark's own pistol, and started over the mountains within days.
When the Corps needed to choose their winter camp location on the Pacific Coast in November 1805, Lewis and Clark held a vote in which every member of the expedition took part, including Sacagawea, a Native woman, and York, Clark's enslaved Black servant.
Clark counted York's vote with the men's and wrote down Sacagawea's preference in a separate note. This was 65 years before the 15th Amendment gave Black men the right to vote and 115 years before the 19th Amendment gave women the right to vote.
Historians have debated what the vote meant. It was not a formal exercise with legal standing, York remained enslaved, and Sacagawea returned to her husband's household after the expedition. As a moment of practical inclusion in American history, though, it stands nearly alone in its era.
Clark's field notes for November 24, 1805 list each person's preference by name, including 'Janey,' his nickname for Sacagawea, who favored a place with 'plenty of' wapato root. It is one of the earliest surviving records of a woman and an enslaved person being polled on a public decision on the North American continent.
As the Corps descended the Columbia in October 1805, they faced a series of violent rapids that Chinookan nations warned were impassable by canoe. The expedition had neither the time nor the provisions for long portages.
Lewis and Clark decided to run the worst rapids directly, sending the non-swimmers and the most valuable papers and equipment around on foot while the experienced rivermen took the canoes through. Crowds of Native people gathered on the banks, apparently expecting the canoes to be destroyed.
The Corps ran the rapids successfully, impressing the river nations and cementing its reputation as extraordinary travelers. The decision saved weeks of travel that would have been critical given the party's dwindling food.
They still had to portage the truly impassable drops, Celilo Falls and the worst of the narrows at The Dalles, carrying canoes and cargo over the rocks while local Wishram and Wasco people helped for pay. Friction over pilfering along this stretch, and the Corps' hard response, soured relations that the men remembered bitterly on the return trip.
Did You Know?
Lewis and Clark documented 178 plants and 122 animals previously unknown to science, including the grizzly bear, the pronghorn antelope, the prairie dog, the western meadowlark, and the bull snake. Lewis sent a live prairie dog, four magpies, and a grouse back to Jefferson on the keelboat in 1805; the prairie dog and one magpie arrived alive.
Congress appropriated $2,500 for the expedition in February 1803, after Jefferson's January request. The actual cost came to approximately $38,000, still considered one of the most extraordinary investments in American history. For $38,000, the United States gained detailed knowledge of its new western territory, established diplomatic relations with dozens of Native nations, and produced maps that guided American expansion for the next 50 years.
The grizzly bear became the expedition's most feared animal. Lewis initially dismissed warnings about grizzlies from Native informants, writing that he doubted the bear could be as dangerous as described. After his first encounter, in which a grizzly charged him and he had to jump into the river to escape, he revised his opinion dramatically. The Corps killed 43 grizzlies over the course of the expedition.
Both Lewis and Clark kept detailed daily journals, as did several enlisted men including Sergeant Patrick Gass, whose account was the first published narrative of the expedition in 1807. Lewis's journals were not published until 1814, five years after his death. The full, authoritative edition of the journals was not published until 1904-1905, the centennial of the expedition.
Clark's maps of the West were so accurate that they remained the primary cartographic reference for the region for decades. His map of 1810 showed the entire route of the expedition with remarkable precision despite having no GPS, no aerial photography, and no survey instruments more sophisticated than a sextant and compass. Modern GPS surveys have confirmed Clark's latitude measurements to within a few miles across thousands of miles of terrain.
Fort Clatsop was one of the most miserable winter encampments in American exploration history. Of the 106 days the Corps spent there from December 1805 to March 1806, only 12 were without rain or fog. The men were perpetually wet, cold, and flea-infested. Elk became scarce and the Corps often went without meat. Lewis wrote that he had never spent a more uncomfortable winter in his life.
Lewis brought an airgun on the expedition, a Girandoni air rifle capable of firing 22 shots on a single charge without powder or ball. The weapon astonished every Native nation that saw it demonstrated. Lewis used it strategically throughout the journey as both a tool of diplomacy and intimidation, allowing him to demonstrate remarkable firepower without revealing the expedition's actual ammunition supply.
Jean-Baptiste Charbonneau, Sacagawea's son born on February 11, 1805 at Fort Mandan, was the youngest member of the expedition and traveled the entire western journey on his mother's back. Clark became fond of the boy, nicknamed him Pompey, and later paid for his education. Jean-Baptiste went on to become a well-traveled frontiersman, spending years in Europe as a guest of a German prince before returning to the American West.
What Lewis and Clark Left Behind
The Corps of Discovery returned to St. Louis on September 23, 1806. The expedition had achieved nearly everything Jefferson had asked of it, except the Northwest Passage, which did not exist. What it had accomplished instead was arguably more valuable: the first accurate map of the American West, the first systematic scientific survey of the continent's interior, the first sustained American diplomatic contact with the nations of the upper Missouri and Pacific Northwest, and a demonstration that the continent was crossable.
The effects of those achievements rippled through American history for the next century. Some were profound and positive. Some were tragic for the peoples the expedition had encountered. All of them were permanent.
Clark's maps transformed American understanding of the West. Before the expedition, the region beyond the Mississippi was a cartographic void, filled by mapmakers with speculation, mythical mountains, and blank space.
Clark produced the first accurate map of the Missouri River to its source, the first accurate depiction of the Continental Divide, and the first American map of the Columbia River system.
His 1810 manuscript map remained the definitive reference for the American West for decades and guided every exploring expedition, military campaign, and emigrant train that followed.
Clark kept refining the master map for years, adding information from fur trappers. The version engraved for the 1814 published account, 'A Map of Lewis and Clark's Track,' fixed the shape of the Rockies, the Columbia system, and the northern Missouri in the public mind and served as the base map of the West until the government surveys of the 1840s and 1850s.
The natural-history record of the expedition was extraordinary. Lewis documented 178 previously unknown plant species and 122 previously unknown animal species with enough accuracy that many of his descriptions remain useful to biologists today.
He collected hundreds of physical specimens, pressed plants, animal skins, skeletal samples, that he sent back to Jefferson and that enriched American natural-history collections.
The scientific work of the Corps of Discovery was among the most productive single field expeditions in the history of American natural history.
Much of the collection was mishandled afterward. Lewis's death in 1809 scattered it; some pressed plants survived at the Academy of Natural Sciences in Philadelphia and were not fully catalogued for a century, and several species Lewis first found were formally named by other botanists. A number still carry the names lewisii or clarkii, among them the bitterroot, Lewisia rediviva, and the wildflower genus Clarkia.
The expedition established direct American government contact with dozens of Native nations for the first time, and the captains' journals gave the most detailed ethnographic record of the upper Missouri and Pacific Northwest nations produced in the early 19th century.
The diplomatic mission was, in the short term, largely successful; the Corps traveled thousands of miles through Native territory with remarkably little violence.
In the long term, the expedition opened the pathway for American expansion that would devastate nearly every nation the Corps had met. The routes, the maps, and the knowledge of resources were all used in the following decades to dispossess the same peoples the Corps had approached as diplomatic partners.
The one violent clash came on the return trip: on July 27, 1806, on the Marias River in Montana, Lewis's small party killed two Blackfeet men in a fight over horses and guns, the only people the Corps killed, and it helped set a Blackfeet hostility toward Americans that lasted a generation.
The Lewis and Clark route did not become a wagon road; the Lolo Trail across the Bitterroots was far too rugged for emigrant wagons.
But the expedition's reports of the fertile Willamette Valley, the navigable lower Columbia, and the abundance of fish and game in the Pacific Northwest fired the American imagination and created the idea of Oregon as a destination worth the journey.
The Oregon Trail, developed in the 1840s, followed a more southerly route pioneered by fur traders, but the belief that the Pacific Northwest was reachable and worth reaching was a direct consequence of Lewis and Clark's reports. Roughly 300,000 emigrants traveled the trail between 1841 and 1869.
The reports also helped make 'Oregon' a national political question. In the 1840s, expansionists used the slogan 'Fifty-Four Forty or Fight' to press a claim to the whole Northwest against Britain; the 1846 Oregon Treaty split the disputed country at the 49th parallel, securing for the United States the future states of Oregon, Washington, and Idaho that the Corps had crossed.
Lewis and Clark's reports of beaver-rich rivers throughout the Rocky Mountain region launched one of the great economic booms in American history. Within a few years of the expedition's return, fur-trading companies were sending men into the mountains along the routes the captains had mapped.
John Jacob Astor founded the Pacific Fur Company in 1810 and established Fort Astoria near the mouth of the Columbia in 1811.
The Rocky Mountain fur trade drove parts of the American economy for three decades, produced the figure of the Mountain Man, and planted a permanent American presence in territory also claimed by Britain, Spain, and Russia.
The trade itself was largely finished within about forty years, as beaver populations crashed and silk hats replaced felt ones in fashion. But the trappers' rendezvous system and the passes they scouted, South Pass through the Rockies above all, became the emigrant roads of the 1840s, and former mountain men such as Jim Bridger and Kit Carson guided the wagon trains and the Army west.
Perhaps the most consequential legacy of Lewis and Clark was ideological. The expedition proved that the continent was crossable, that American citizens could travel from the Mississippi to the Pacific and return, and that the West was not the vast featureless desert some had imagined.
Jefferson's vision of a continental American republic stretching from sea to sea went from a dream to a demonstrated possibility.
The expedition became central to the American story of westward expansion, and the belief that American expansion across the continent was inevitable, and even divinely sanctioned, drew much of its energy from the Corps' success.
The phrase 'manifest destiny' itself was coined only in 1845, by the journalist John L. O'Sullivan, decades after the expedition, but writers reaching for the idea consistently traced it back to Jefferson's project. The centennial of 1904 to 1906, marked by a world's fair in Portland and the first scholarly edition of the journals, fixed Lewis and Clark as founding figures of the national story of the West.
What Happened to the People
Meriwether Lewis
Jefferson appointed Lewis Governor of Louisiana Territory after the expedition. He struggled with the administrative role, fell into debt, and suffered from severe depression. He died on October 11, 1809, at Grinder's Stand on the Natchez Trace, his wounds were gunshot wounds to the head and chest. Jefferson and Clark both concluded it was suicide. The journals Lewis had promised to publish were never prepared during his lifetime.
William Clark
Clark thrived after the expedition. He served as Superintendent of Indian Affairs for the Missouri Territory and later as Governor of Missouri Territory. He drew the expedition's master map around 1810; it was published in the 1814 Biddle edition of the journals. He maintained relationships with many Native leaders he had met on the expedition and was considered a relatively honest and fair Indian Agent by the standards of his era. He died in 1838 at age 68.
Sacagawea
The historical record diverges sharply. Most primary sources indicate Sacagawea died in 1812 at Fort Manuel in present-day South Dakota, probably of typhoid fever, at approximately age 24. However, oral traditions of the Comanche and Shoshone nations, supported by some documentary evidence, describe a woman matching her description living on the Wind River Reservation in Wyoming until 1884. The question has never been definitively resolved.
York
York continued to press Clark for his freedom after the expedition. Clark reportedly freed him sometime between 1811 and 1816. Some accounts indicate York attempted to operate a freighting business in Kentucky and Tennessee that failed. Clark later told a visitor that York had died of cholera while trying to reach St. Louis. Other accounts, possibly based on the testimony of frontiersman Zenas Leonard, suggest York returned west and lived among the Crow Nation. His ultimate fate is unknown.
Jean-Baptiste Charbonneau
Sacagawea's son, born on the expedition, became one of the most widely traveled Americans of the 19th century. Clark paid for his education in St. Louis. At 18, he traveled to Europe with German Prince Paul of Wurttemberg, spending six years in Germany, France, and North Africa. He returned to America and became a mountain man, guide, and interpreter in the fur trade era. He died in 1866 in present-day Oregon, having been born in present-day North Dakota on the very expedition that opened the West.
Visit the Trail Today
The Lewis and Clark National Historic Trail follows the expedition route for nearly 4,900 miles across 16 states, from Pittsburgh, Pennsylvania, to the Pacific coast of Oregon. Hundreds of sites along the trail are open to the public.
Fort Clatsop
Astoria, Oregon, reconstructed winter fort, National Park Service site
Pompeys Pillar
Billings, Montana, sandstone butte where Clark carved his signature on July 25, 1806, the only physical evidence of the expedition remaining on the landscape
Fort Mandan
Washburn, North Dakota, reconstructed winter fort near the Mandan-Hidatsa villages
Great Falls
Great Falls, Montana, the five cascades that required a portage of roughly a month, still visible today
Lemhi Pass
Montana-Idaho border, the continental divide crossing point where Lewis saw more mountain ranges stretching west to the horizon
Sources & Further Reading
- Lewis and Clark National Historic Trail, National Park Service
- Lewis and Clark Expedition Collection, Library of Congress
- The Journals of the Lewis and Clark Expedition, University of Nebraska-Lincoln
- Lewis & Clark, The Journey of the Corps of Discovery, PBS / Ken Burns
- Louisiana Purchase Treaty, 1803, National Archives
- Discovering Lewis & Clark, Lewis and Clark Trail Alliance