From a Warning Letter to a Multi-Trillion-Dollar Arsenal
It began with a single letter to a president and grew into the largest industrial construction effort in American history, then into a permanent, decades-long feature of national life. What follows is every major milestone in order.
The American nuclear program did not start with a single decision. It grew step by step, from a warning about German research in 1939, to a secret wartime construction project that displaced whole farming communities, to a permanent Cold War arsenal, and eventually to a civilian power industry built on the same underlying science.
What follows is sourced to the Department of Energy's Office of Legacy Management, the National Park Service, the Nuclear Regulatory Commission, the Brookings Institution, and the Federation of American Scientists, tracing every major milestone from the first shovel in the ground to today's stockpile.
Every Milestone, Start to Today
In December 1938, German chemists Otto Hahn and Fritz Strassmann split a uranium atom in a Berlin laboratory, and physicists Lise Meitner and Otto Frisch worked out weeks later that the reaction released enormous energy, a process they named nuclear fission.
News of the discovery spread quickly through the international physics community in early 1939, and scientists on several continents immediately recognized its military potential. Meitner, an Austrian Jew who had fled to Sweden months earlier, was never credited by the Nobel committee, which gave the chemistry prize to Hahn alone.
Alarmed that Nazi Germany might build a fission weapon first, physicists Leo Szilard and Eugene Wigner drafted a letter for Albert Einstein's signature warning President Franklin Roosevelt of the danger.
Roosevelt received the letter on October 11, 1939, and authorized a small Uranium Committee to study the question, a modest first step, its first federal grant was just $6,000, that would grow within three years into the largest industrial construction project the United States had ever undertaken.
The U.S. Army Corps of Engineers formally established the Manhattan Engineer District in August 1942 and placed Brig. Gen. Leslie Groves in command the following month, giving him near-total authority over budgets, land acquisition, and industrial contracts with almost no congressional oversight.
Groves, who had just finished overseeing construction of the Pentagon, moved immediately to secure three remote sites: a farming valley in eastern Tennessee, a stretch of scrubland along the Columbia River in Washington State, and a mesa in northern New Mexico, each chosen for isolation, water and power access, and distance from the coasts.
Bulldozers broke ground at the Tennessee site, soon named Oak Ridge, in the fall of 1942, displacing roughly 1,000 farm families under wartime condemnation orders, while construction crews began work at Hanford in early 1943 and at the Los Alamos laboratory site that same spring.
Within eighteen months these three secret communities grew to house tens of thousands of workers, none of whom were told what they were building. At its peak the project employed roughly 130,000 people and, adjusted for inflation, spent more over three years than the entire U.S. automobile industry did during the war.
On December 2, 1942, physicist Enrico Fermi and his team achieved the world's first controlled, self-sustaining nuclear chain reaction inside Chicago Pile-1, a crude stack of graphite blocks and uranium built underneath the stands of an unused University of Chicago football field.
The experiment proved a chain reaction could be controlled rather than simply exploding, and its success cleared the way for full-scale plutonium production reactors. Physicist Arthur Compton reported it to Washington in code: 'The Italian navigator has landed in the New World.'
At Oak Ridge, the Manhattan Project raced to enrich uranium using three competing and unproven methods at once, electromagnetic separation, gaseous diffusion, and thermal diffusion, rather than waiting to see which would work. The Y-12 plant's calutrons were run around the clock largely by young women recruited locally, later nicknamed the Calutron Girls, trained to watch dials without being told what the machines produced.
Oak Ridge alone consumed about $1.2 billion, 63 percent of the entire Manhattan Project budget, according to Department of Energy cost records analyzed by the Brookings Institution. Its K-25 gaseous diffusion plant was, when finished, the largest building in the world under one roof.
At the Hanford site in Washington State, DuPont engineers built the world's first full-scale plutonium production reactor, B Reactor, in just over a year, going critical in September 1944.
The reactor used water from the Columbia River for cooling and irradiated uranium fuel slugs to breed plutonium, which chemical processing plants elsewhere on the sprawling 586-square-mile site then extracted and purified. When B Reactor first started up it unexpectedly poisoned itself and shut down within hours, an effect the physicist John Wheeler had anticipated, and DuPont's decision to build in hundreds of extra fuel tubes let it be restarted.
Hanford ultimately grew to include nine production reactors and several massive chemical separation plants, all built and operated in near-total secrecy; most of the roughly 50,000 workers on-site had no idea they were manufacturing bomb material.
The plutonium made at Hanford fueled the Trinity test and the Nagasaki bomb and later became the foundation of the Cold War arsenal, a legacy that also left Hanford as the most contaminated nuclear site in the Western Hemisphere, with 56 million gallons of radioactive waste in aging underground tanks, some of which have leaked.
At 5:29 a.m. on July 16, 1945, scientists at the Los Alamos laboratory, led by physicist J. Robert Oppenheimer, detonated the world's first nuclear device atop a 100-foot steel tower in the Jornada del Muerto desert near Alamogordo, New Mexico.
The plutonium implosion device, nicknamed 'the Gadget,' released an estimated 21 kilotons of explosive energy (a 2021 Los Alamos reanalysis put it at about 25 kilotons), vaporized the tower entirely, and fused the desert sand below into a glassy green mineral later named trinitite. A few scientists had privately bet on yields as low as zero; physicist Isidor Rabi won a betting pool by guessing 18 kilotons.
Gen. Leslie Groves and Oppenheimer inspected ground zero within hours, and Manhattan Project leaders immediately reported the successful test to President Harry Truman, who was at the Potsdam Conference with Soviet and British leaders. Truman mentioned only vaguely to Stalin that the U.S. had a powerful new weapon; Soviet spies had already told Stalin about the program in detail.
Combined with the rest of the Manhattan Project's three years of work, the effort had cost roughly $2 billion, more than $28 billion today, and Trinity remains the only large-scale field test of a U.S. nuclear weapon design before combat use. Fallout drifted over nearby ranches whose residents were not warned, and were added to the federal compensation program only in 2025.
On August 6, 1945, the U.S. Army Air Forces dropped the uranium gun-type bomb Little Boy on Hiroshima, and three days later dropped the plutonium implosion bomb Fat Man on Nagasaki, the only two nuclear weapons ever used in armed conflict.
The Department of Energy's Office of History and the National Park Service estimate the combined immediate and short-term deaths from both bombings at well over 100,000 people, with tens of thousands more dying in later years from radiation-related illness. Hiroshima's yield was about 15 kilotons and Nagasaki's about 21.
Little Boy's gun design was considered so reliable that it was never tested before use; Fat Man used the same implosion design proven at Trinity. Nagasaki was a secondary target, bombed after clouds obscured the primary, the city of Kokura.
Japan announced its intention to surrender on August 15, 1945, and signed the formal instrument aboard the USS Missouri on September 2, ending World War II. Historians still debate how much the bombs, versus the Soviet declaration of war on Japan on August 8, drove the surrender; the bombings nonetheless made nuclear weapons the central strategic fact of the postwar world.
President Truman signed the Atomic Energy Act, commonly called the McMahon Act, on August 1, 1946, stripping the military of direct control over the nation's atomic program and transferring authority to a new civilian Atomic Energy Commission, effective January 1, 1947.
The law reflected a deliberate postwar decision that nuclear weapons and nuclear science were too consequential to leave under exclusive military command, even as the AEC absorbed all of the Manhattan Project's plants, personnel, and secrecy culture intact. An earlier draft, the May-Johnson bill, would have kept the program under heavy military influence; scientists lobbied Congress hard to defeat it.
The Act made all nuclear technology and 'restricted data' government property by default, the only category of information in U.S. law treated as 'born secret,' and it barred sharing weapons information even with wartime allies such as Britain.
The AEC took on a dual and, in hindsight, conflicted mission from the outset: it was simultaneously responsible for building and testing nuclear weapons and for promoting the peaceful use of nuclear energy, while also serving as the industry's sole safety regulator. That built-in conflict of interest went unresolved for nearly three decades.
The Soviet Union detonated its first atomic device, called First Lightning by the Soviets and Joe-1 by American intelligence, at its Semipalatinsk test site in Kazakhstan on August 29, 1949, four years earlier than most American analysts had predicted.
The device was a close copy of the Fat Man design, built with help from espionage: the physicist Klaus Fuchs, who had worked at Los Alamos, had passed detailed implosion designs to Moscow.
U.S. intelligence detected the test through airborne radiation sampling, and the news, made public in September 1949, ended the four-year American nuclear monopoly and set off a decades-long arms race.
President Truman responded in January 1950 by authorizing an accelerated program to develop a far more powerful thermonuclear, or hydrogen, weapon, over the objections of several Manhattan Project veterans, including Oppenheimer, who feared unrestrained escalation. The decision made the American nuclear program a permanent element of national defense rather than a wartime emergency.
The United States detonated the world's first full-scale thermonuclear device, Ivy Mike, at Enewetak Atoll in the Pacific on November 1, 1952, releasing roughly 10.4 megatons, nearly 700 times the yield of the Hiroshima bomb, and completely vaporizing the small island of Elugelab.
Ivy Mike was not a usable weapon: it was a building-sized apparatus that used liquid deuterium kept cold by a refrigeration plant. The test confirmed that fusion weapons could reach yields far beyond any fission bomb, and both superpowers raced to build dry, deliverable versions; the Soviet Union tested its first true deliverable thermonuclear bomb in 1955.
On March 1, 1954, the Castle Bravo test at Bikini Atoll produced an accidental 15-megaton yield, roughly two and a half times its designers' prediction, because they had miscalculated the reactivity of an isotope of lithium in the fuel, spreading fallout over a far larger area than planned.
Fallout sickened Marshall Islanders on Rongelap and Utirik atolls, who were evacuated only after significant exposure, and dusted the Japanese fishing boat Daigo Fukuryu Maru (Lucky Dragon 5) with radioactive ash that caused acute radiation sickness and, within months, the death of one crewman, an incident that triggered global alarm over atmospheric testing and helped inspire that year's original 'Godzilla' film.
President Eisenhower's December 1953 Atoms for Peace speech to the United Nations called for channeling nuclear technology toward civilian energy, and Congress followed with the Atomic Energy Act of 1954, which for the first time let private companies, not only the government, own and operate reactors.
Congress also passed the Price-Anderson Act in 1957, capping the nuclear industry's accident liability, a subsidy regulators judged necessary because no private insurer would underwrite the full risk of a new technology. Price-Anderson has been renewed repeatedly and is still in force.
The Shippingport Atomic Power Station near Pittsburgh, Pennsylvania, began supplying electricity to the commercial grid in December 1957, the first full-scale civilian nuclear power plant in the United States. Its reactor was a scaled-up version of the pressurized-water design Admiral Hyman Rickover had developed for nuclear submarines.
Utilities across the country soon placed their own reactor orders, launching an industry that would eventually supply about one-fifth of all U.S. electricity, built on infrastructure and expertise first developed for weapons and naval propulsion. Reactor orders peaked in the early 1970s and then collapsed after cost overruns and the 1979 Three Mile Island accident.
The Nevada Test Site, opened in 1951 roughly 65 miles from Las Vegas, hosted around 100 above-ground nuclear detonations over the following decade, with fallout regularly drifting northeast across rural Utah, Nevada, and Arizona.
Communities in the fallout path, later known as downwinders, saw documented increases in thyroid cancer, leukemia, and other radiation-linked illnesses that the federal government did not officially acknowledge for decades. The AEC publicly assured residents the tests were safe, and Las Vegas casinos advertised rooftop views of the mushroom clouds as a tourist draw.
A 1997 National Cancer Institute study estimated that iodine-131 fallout from Nevada testing exposed the American public to enough radiation to cause tens of thousands of extra thyroid-cancer cases nationwide, well beyond the immediate downwind area.
International alarm after Castle Bravo, and mounting evidence of fallout harm, led the United States, the United Kingdom, and the Soviet Union to sign the Partial Test Ban Treaty in August 1963, banning tests in the atmosphere, underwater, and in space while still allowing underground testing, which the United States continued at the Nevada Test Site for another three decades.
The United States, the Soviet Union, and dozens of other nations opened the Treaty on the Non-Proliferation of Nuclear Weapons for signature in July 1968. Recognized nuclear-armed states pledged to pursue disarmament, and non-nuclear states pledged never to acquire weapons in exchange for access to peaceful nuclear technology.
The treaty entered into force in 1970 and remains the cornerstone of the global nonproliferation system, with 191 states parties, more than almost any other arms agreement. Only India, Pakistan, Israel, South Sudan, and North Korea, which withdrew in 2003, stand outside it.
The NPT did not slow American or Soviet weapons production in the near term, and the two arsenals kept growing through the late 1960s; the U.S. stockpile alone peaked at 31,255 warheads in fiscal year 1967, a figure the Department of Energy formally declassified in 2010.
But the treaty built the legal and diplomatic architecture that every later arms control agreement, from SALT to New START, would rest on, and its five-year review conferences remain the main venue where nuclear and non-nuclear states hold each other to account.
After years of criticism that the AEC could not credibly regulate an industry it was also promoting, Congress passed the Energy Reorganization Act of 1974, which President Ford signed on October 11, 1974.
The law abolished the AEC entirely and split its functions between two new agencies: the independent Nuclear Regulatory Commission, which took over civilian reactor licensing and safety oversight, and the Energy Research and Development Administration, which took over nuclear weapons production and broader energy research.
Both agencies began operating on January 19, 1975, ending the AEC's 28-year run as both promoter and regulator. Pressure had been building since a 1971 federal appeals-court ruling, the Calvert Cliffs decision, forced the AEC to weigh environmental impacts in licensing for the first time.
The reorganization created no new safety rule on its own, but it removed the structural conflict of interest that critics, including members of Congress, argued was incompatible with rigorous, independent oversight of a technology with catastrophic failure potential. The Joint Committee on Atomic Energy, long the program's powerful congressional patron, was itself abolished in 1977.
Facing the 1970s energy crisis, President Carter signed the Department of Energy Organization Act in August 1977, consolidating the Energy Research and Development Administration, the Federal Energy Administration, and parts of several other agencies into a single new cabinet department.
The Department of Energy formally began operations on October 1, 1977, inheriting ERDA's nuclear weapons design, production, and testing responsibilities alongside a much broader civilian energy mission. James Schlesinger, a former Defense Secretary and AEC chairman, became its first secretary.
For the first time, the same cabinet department that funded basic energy research and set national energy policy also owned and operated the entire nuclear weapons production complex, Los Alamos, Oak Ridge, Hanford, Savannah River, Rocky Flats, and the Pantex final assembly plant in Texas among them.
That arrangement, weapons production nested inside a civilian energy department rather than the Pentagon, remains in place today through the Department of Energy's semi-autonomous National Nuclear Security Administration, and weapons activities still make up roughly half of the department's budget.
In the early morning hours of March 28, 1979, a stuck-open relief valve combined with equipment failures and operator errors to cause a partial meltdown of the Unit 2 reactor core at the Three Mile Island Nuclear Generating Station near Middletown, Pennsylvania.
The Nuclear Regulatory Commission's own backgrounder concludes that the small radioactive releases that escaped the containment building caused no detectable health effects on plant workers or the public, though a two-day advisory for pregnant women and small children to leave the area caused widespread alarm.
The accident coincided almost exactly with the release of the film 'The China Syndrome,' about a fictional reactor near-disaster, which sharpened public fear. A presidential commission later blamed inadequate operator training and confusing control-room design as much as the equipment itself.
The accident, the most serious in the history of American commercial nuclear power, triggered sweeping NRC changes to operator training, emergency planning, and control-room design, and it effectively halted new domestic reactor orders for more than three decades. No new nuclear plant construction would break ground in the United States until the Vogtle expansion in 2009.
As U.S.-Soviet relations thawed in the late 1980s, President Reagan and Soviet leader Mikhail Gorbachev signed the Intermediate-Range Nuclear Forces Treaty in 1987, eliminating an entire class of ground-launched missiles for the first time in history.
The INF Treaty scrapped roughly 2,700 missiles with ranges between 500 and 5,500 kilometers and introduced on-site inspections that were unprecedented in their intrusiveness. The United States withdrew from the treaty in 2019, citing Russian violations.
Presidents George H.W. Bush and Boris Yeltsin followed with the Strategic Arms Reduction Treaty (START I), signed in 1991, the first legally binding cuts in strategic nuclear warheads. Bush also ordered unilateral steps in 1991, pulling most tactical nuclear weapons off ships and out of Europe.
The collapse of the Soviet Union that same year removed the singular threat that had justified the arsenal's Cold War scale, and administrations of both parties began steadily retiring warheads and closing production plants. The U.S. stockpile, which had peaked at 31,255 warheads in 1967, was already down to roughly 20,000 by the early 1990s and has kept shrinking since.
On June 6, 1989, more than 70 FBI and EPA agents raided the Rocky Flats plutonium trigger plant near Denver, Colorado, the first time one federal agency had raided a facility operated on behalf of another.
A two-year investigation had found that Rockwell International, the plant's operating contractor, had been violating federal environmental laws for years while both the contractor and Department of Energy officials certified the facility as in compliance. A special grand jury later recommended indicting individuals; the Justice Department instead settled with Rockwell for an $18.5 million fine in 1992, and the grand jury's report was sealed.
Plutonium production at Rocky Flats never resumed after the raid; the Secretary of Energy formally suspended operations later that year after dangerous plutonium accumulations were found in the ventilation ducts.
The site underwent a $7 billion Superfund cleanup that the EPA declared complete in 2005, and in 2007 most of the 6,300-acre former plant became the Rocky Flats National Wildlife Refuge, which opened to the public in September 2018, a designation still contested by some neighbors and former workers who question whether residual contamination makes public recreation safe.
The United States conducted its 1,030th and final full-scale underground nuclear test, code-named Divider, at the Nevada Test Site on September 23, 1992, and Congress that year enacted a moratorium on further U.S. testing that President George H.W. Bush signed into law.
Every president since has kept the moratorium on explosive testing. In October 2025 President Trump directed the Pentagon to begin testing nuclear weapons "on an equal basis" with other countries; officials later described the planned tests as non-explosive system tests. No American nuclear weapon has been physically detonated in a test since 1992.
Negotiators completed the Comprehensive Nuclear-Test-Ban Treaty in 1996, banning all nuclear explosions everywhere, and President Clinton was the first world leader to sign it. But the U.S. Senate rejected ratification 51 to 48 in 1999, and the treaty has never entered into force because several required states, including the United States and China, have not ratified.
The United States nonetheless keeps observing its voluntary moratorium, relying instead on the Stockpile Stewardship Program's laboratory experiments and supercomputer simulations to certify that its warheads still work. Weapons-lab directors have repeatedly said simulation now gives them more confidence than a single new test would.
A wave of security controversies at Los Alamos in the late 1990s, including the Wen Ho Lee espionage investigation and repeated findings of lax accounting for classified material, convinced Congress that the Department of Energy's weapons complex needed a more focused, accountable management structure.
Wen Ho Lee, a Taiwanese-American scientist, was held in solitary confinement for months on 59 felony counts; the case collapsed, and he pleaded guilty to a single count of mishandling data, drawing an unusual apology from the federal judge.
The National Defense Authorization Act for fiscal year 2000 created the National Nuclear Security Administration as a semi-autonomous agency inside the Department of Energy, and it began operating in March 2000.
The NNSA, not the Department of Energy directly, has managed the entire weapons production and design complex, the national laboratories, and the naval nuclear propulsion program ever since, while still reporting through the Secretary of Energy to the President. It handles essentially every weapons-related dollar Congress appropriates today, roughly $19 billion in fiscal 2024.
Congress narrowed its search for a permanent national nuclear waste repository to a single site in 1987, designating Yucca Mountain, Nevada, over strong objections from the state, in an amendment Nevadans nicknamed the 'Screw Nevada bill.'
The Department of Energy spent the following two decades studying the site and submitted a formal license application in 2008. The facility was meant to permanently store spent fuel from commercial reactors and high-level waste from the weapons complex deep inside a desert ridge roughly 100 miles from Las Vegas.
The Obama administration moved to halt funding and withdraw the license application in 2010, and Congress has not appropriated construction money since, even though the Nuclear Waste Policy Act still legally names Yucca Mountain as the nation's sole repository site.
More than $15 billion has been spent studying and licensing a facility that has never opened. Reactor and weapons waste sits in temporary storage at dozens of sites nationwide, and utilities have won court judgments now totaling billions of dollars against the federal government for missing the 1998 deadline the law set for it to begin accepting spent fuel.
With underground testing off the table after 1992, the Department of Energy launched the Stockpile Stewardship Program in 1995 to certify that aging warheads remained safe and reliable using supercomputer simulations, subcritical experiments, and laboratory-scale fusion research rather than full detonations.
The centerpiece of that effort, the National Ignition Facility at Lawrence Livermore National Laboratory in California, began construction in the 1990s and started operating in 2009, focusing 192 laser beams onto a target smaller than a pea. It came in years late and about four times over its original budget, drawing sustained criticism from government auditors.
On December 5, 2022, NIF scientists achieved fusion ignition for the first time in any laboratory, delivering 2.05 megajoules of laser energy that produced 3.15 megajoules of fusion energy, a net energy gain Lawrence Livermore called the culmination of more than 60 years of inertial confinement fusion research.
The milestone was funded and pursued mainly to support the NNSA's stockpile certification mission, giving scientists data on how fusion fuel behaves in conditions like those inside a detonating weapon, though it also advanced the long-term prospect of fusion power. NIF has since repeated and exceeded the result.
Georgia Power broke ground on two new Westinghouse AP1000 reactors, Vogtle Units 3 and 4, in 2009, the first new commercial nuclear construction project in the United States since Three Mile Island had frozen the industry in 1979.
The project was originally estimated at about $14 billion and due to finish by 2016 and 2017, backed in part by more than $12 billion in Department of Energy loan guarantees, at the time the largest federal loan guarantee ever issued for a single project. A sister project in South Carolina, V.C. Summer, was abandoned in 2017 after $9 billion was spent and no reactor was finished.
Plagued by design changes, the 2017 bankruptcy of Westinghouse, and pandemic-era supply disruptions, Vogtle ultimately took fifteen years and cost roughly $36.8 billion, more than two and a half times the original estimate.
Unit 3 entered commercial service in July 2023 and Unit 4 in the spring of 2024. Georgia regulators approved rate increases passing much of the overrun to ratepayers, and the project is now widely cited as a cautionary example of the cost and schedule risk in building large new reactors, one reason industry interest has shifted toward smaller modular designs.
Beginning in the early 2020s, the Pentagon launched a simultaneous, multi-decade overhaul of all three legs of the nuclear triad: the Columbia-class ballistic missile submarine to replace the aging Ohio class, the B-21 Raider stealth bomber to eventually replace the B-2 and B-1, and the Sentinel intercontinental ballistic missile to replace the 1970s-era Minuteman III.
The B-21 completed its first flight in November 2023 and is planned in a fleet of at least 100 aircraft; the first Columbia-class submarine is under construction and due to begin patrols around 2031, at a cost of roughly $9 billion per boat.
The Sentinel program alone triggered a formal Nunn-McCurdy cost breach in January 2024 after its projected cost grew to nearly $141 billion, an 81 percent increase over its original 2020 estimate of about $78 billion, driven largely by the expense of rebuilding hundreds of launch facilities and control centers across five states rather than the missile itself.
Pentagon leadership certified the program to continue in July 2024 despite the overrun, arguing no viable alternative existed to replace an ICBM force approaching 60 years old. Some former officials have argued the land-based leg could be retired entirely, but that view has never had majority support in Congress.
The Radiation Exposure Compensation Act, which had paid more than $2.6 billion to over 41,000 downwinders, uranium workers, and other radiation victims since 1990, expired on June 7, 2024, after Congress failed to renew it, cutting off new claims from communities still awaiting compensation.
Congress revived and expanded the program in July 2025, broadening eligible locations, adding areas near the Trinity site in New Mexico and additional Western communities, and increasing payment amounts, though gaps in coverage for some affected groups remain a subject of ongoing advocacy.
The New START treaty, the last remaining agreement capping American and Russian deployed strategic warheads, expired on February 5, 2026, after Russia suspended its participation in 2023 and the two sides did not negotiate a replacement treaty (Russia had offered in September 2025 to keep observing the limits for a year if the United States did the same), leaving the two largest nuclear arsenals unconstrained by any bilateral treaty for the first time since 1972.
The Federation of American Scientists estimates the U.S. stockpile at roughly 3,700 warheads, active and inactive, plus about 1,477 retired warheads awaiting dismantlement, a small fraction of the 1967 peak but still backed by a modernization program the Congressional Budget Office projected in April 2025 at about $946 billion for 2025 to 2034.
A Wartime Emergency Project Became Permanent Infrastructure
The sites, laboratories, and delivery systems built for the Manhattan Project never went away. They were consolidated, modernized, and, since 1992, run without a single actual test explosion.
The National Laboratories Design It
Los Alamos and Lawrence Livermore national laboratories design and certify every U.S. nuclear warhead, while Sandia National Laboratories engineers the non-nuclear components, arming systems, and safety mechanisms around them.
All three are owned by the federal government but run day to day by private contractor teams under National Nuclear Security Administration oversight, a 'government-owned, contractor-operated' model carried over almost unchanged from the Manhattan Project.
Having two competing weapons-design labs, Los Alamos since 1943 and Livermore since 1952, is deliberate: each is expected to check and challenge the other's work, a form of built-in peer review for designs that can no longer be tested.
A Smaller, Consolidated Production Complex
Today's weapons production complex is far smaller than its Cold War peak. The Pantex Plant in Texas handles final assembly, disassembly, and life-extension work on every warhead in the stockpile; the Y-12 National Security Complex in Oak Ridge still processes enriched-uranium components; the Savannah River Site in South Carolina supports tritium production; and the Kansas City National Security Campus builds non-nuclear parts.
Rocky Flats' job of manufacturing plutonium 'pits,' the fissile cores of modern warheads, has never been fully replaced since the plant closed in 1989.
Restarting large-scale pit production, split between Los Alamos and a converted plutonium plant at Savannah River, is a central and costly piece of current modernization plans, with a target of 80 pits a year that has repeatedly slipped.
Stockpile Stewardship Instead of Test Explosions
Since the 1992 testing moratorium, no U.S. warhead design has been proven by an actual nuclear detonation.
The Stockpile Stewardship Program instead certifies warhead reliability using supercomputer simulations, subcritical experiments at the Nevada National Security Site that stop short of a self-sustaining chain reaction, and laser-driven fusion experiments at the National Ignition Facility.
Each year the directors of the three weapons labs and the head of U.S. Strategic Command must personally certify to the President that the stockpile remains safe and reliable without testing; they have done so every year since 1996.
The program also leans on archived data from the 1,030 U.S. tests conducted before 1992, which is one reason that data is still carefully preserved and much of it remains classified.
Life Extension Programs, Not New Bombs
Rather than designing new warheads from scratch, the NNSA runs Life Extension Programs that disassemble aging warheads, replace degraded components such as tritium reservoirs and high explosives, and reassemble them under strict configuration control.
The B61-12 gravity bomb and the W88 submarine warhead are both examples of decades-old designs being refurbished and re-certified for continued service rather than replaced outright.
The policy of not developing warheads with new military capabilities has held across administrations of both parties since the mid-1990s, though newer efforts such as the W93 warhead have prompted debate over where refurbishment ends and new design begins.
Delivering the Arsenal: The Nuclear Triad
Warheads are useless without delivery systems, and the United States maintains three: land-based Minuteman III intercontinental ballistic missiles (being replaced by the new Sentinel missile), Ohio-class ballistic missile submarines (being replaced by the Columbia class), and long-range bombers, the B-52 and B-2 today, to be joined by the B-21 Raider.
About 400 Minuteman III missiles sit in underground silos across Montana, North Dakota, Wyoming, Colorado, and Nebraska; up to 14 Ohio-class submarines each carry 20 missiles with multiple warheads; and the bombers are based in Missouri, North Dakota, and Louisiana.
Maintaining three redundant delivery paths, rather than one or two, has been official U.S. policy since the early Cold War specifically so that no single technological or strategic surprise could disarm the country. The submarines, hard to find at sea, are considered the most survivable leg.
Building and Licensing a Commercial Reactor
Civilian nuclear power plants are privately owned and operated but need a construction and operating license from the Nuclear Regulatory Commission, a process that includes detailed safety, seismic, and environmental review before a utility can pour concrete.
Nearly all U.S. commercial reactors use one of two designs, pressurized-water reactors or boiling-water reactors, both descended from 1950s naval and government prototypes.
The industry's most recent build, Vogtle Units 3 and 4 in Georgia, took fifteen years from groundbreaking to commercial operation and cost about two and a half times its estimate, showing how much harder large reactor construction has become since the 1970s boom.
That experience has shifted interest toward small modular reactors, factory-built units of a few hundred megawatts or less that the NRC began licensing in the 2020s, though none is yet operating commercially in the United States.
Decommissioning and the Waste That Has Nowhere to Go
When a commercial reactor retires, its owner must either dismantle it immediately or place it in a decades-long dormancy period before decontamination, all funded through a decommissioning trust fund the utility builds up during the plant's operating life.
The NRC gives operators up to 60 years to finish, and a specialized decommissioning industry has grown up to buy shut-down plants and dismantle them for the trust-fund balance.
Because Yucca Mountain was never completed, every retired reactor's spent fuel, and all of the weapons complex's high-level waste, remains in temporary dry-cask storage or underground tanks on-site, with no permanent national repository under construction anywhere in the country.
About 90,000 metric tons of commercial spent fuel are now stranded at some 75 sites in 35 states, growing by roughly 2,000 tons a year, while the federal government pays utilities court-ordered damages for failing to remove it.
What It Has Cost, and What It Still Costs
From a $1.9 billion wartime project to a $5.48 trillion Cold War total to hundreds of billions still being spent every decade on cleanup and modernization, figures below reflect publicly reported and federally sourced estimates.
| Item | Timeline | Reported Cost | Note |
|---|---|---|---|
| The Manhattan Project | 1942 to 1946 | About $1.9 to $2 billion (1945 dollars), roughly $28 billion today | Oak Ridge alone consumed $1.2 billion, 63 percent of the total, according to Department of Energy records cited by the Brookings Institution. |
| Total U.S. nuclear weapons spending | 1940 to 1996 | $5.48 trillion (1996 dollars) | The Brookings Institution's 1998 Atomic Audit study, led by Stephen Schwartz, found this equaled about 29 percent of all U.S. military spending over the same period, covering research, production, testing, delivery systems, waste management, and environmental cleanup. |
| Rocky Flats environmental cleanup | 1989 to 2005 | About $7 billion | Covered demolition and remediation of the former plutonium trigger plant following its 1989 closure; the site became a national wildlife refuge in 2007 and opened to visitors in 2018. |
| Hanford Site cleanup, lifecycle estimate | Ongoing through at least 2086 | $364 billion to $589 billion | The Department of Energy's 2025 Hanford Lifecycle Scope, Schedule, and Cost Report gives this as its low-to-high range; some environmental monitoring is projected to continue until 2100. |
| NNSA weapons activities, annual budget | Fiscal year 2024 to 2025 | $19.1 billion (FY2024), $19.9 billion requested (FY2025) | Covers the national laboratories, production plants, and stockpile stewardship program; outyear budget projections show continued annual growth toward the mid-$20 billions. |
| Ten-year cost of U.S. nuclear forces | 2023 to 2032 (CBO projection) | $756 billion | The Congressional Budget Office's 2023 estimate was 19 percent higher than its own 2021 estimate of $634 billion for a similar ten-year window, reflecting rising modernization costs across the Pentagon and NNSA; its April 2025 projection rose to about $946 billion for 2025 to 2034. |
| Sentinel ICBM program | 2020 estimate versus 2024 revised cost | Grew from about $78 billion to $141 billion | An 81 percent overrun that triggered a formal Nunn-McCurdy cost-breach review in 2024; the Pentagon certified the program to continue rather than cancel it. |
| Vogtle Units 3 and 4 | 2009 to 2024 | Grew from about $14 billion to $36.8 billion | Backed by more than $12 billion in Department of Energy loan guarantees; Georgia regulators approved rate increases shifting much of the overrun to ratepayers. |
| Yucca Mountain repository | 1987 to 2010, unopened | More than $15 billion spent; about $12 million a year today | Construction funding stopped in 2010; the remaining annual spending covers only site security, legacy data upkeep, and legal costs, not construction. |
Downwinders, Contamination, and an Arsenal Built in Secret
Presented neutrally, with the documented facts on fallout exposure, environmental contamination, the Atomic Energy Commission's conflict of interest, and the current state of arms control.
For more than a decade of above-ground testing at the Nevada Test Site, fallout drifted across rural Utah, Nevada, and Arizona, communities later known as downwinders, without residents being warned of the risk. Documented increases in thyroid cancer and leukemia in these areas led Congress to pass the Radiation Exposure Compensation Act in 1990, which paid more than $2.6 billion to over 41,000 claimants, including downwinders and uranium miners, before the program's authorization lapsed on June 7, 2024. Congress revived and expanded the program in July 2025, though some affected communities, including certain Native American uranium mining families, have argued coverage still leaves gaps.
The Marshall Islands bore a similar burden overseas: the United States conducted 67 nuclear tests at Bikini and Enewetak atolls between 1946 and 1958, permanently displacing residents, and the 1954 Castle Bravo test's unexpectedly large fallout plume caused acute radiation sickness among Rongelap and Utirik islanders who were not evacuated until after significant exposure. Many Marshallese families were never able to permanently resettle their home atolls, and the islands remain a subject of ongoing U.S. compensation agreements today.
Inside the weapons complex itself, decades of Cold War secrecy allowed serious environmental and safety violations to go undisciplined for years, most visibly at Rocky Flats, where a 1989 FBI raid revealed the operating contractor had been violating federal environmental law while both it and Department of Energy officials certified compliance. Hanford, the site that produced the plutonium for the Nagasaki bomb and the bulk of the Cold War arsenal, left behind 56 million gallons of radioactive waste in aging underground tanks, some of which have leaked, a cleanup the Department of Energy now projects will cost up to $589 billion and continue for six more decades.
The Atomic Energy Commission's original dual role, promoting nuclear power while also regulating its safety, was widely criticized as an inherent conflict of interest and was dissolved in the 1974 to 1975 split that created the independent Nuclear Regulatory Commission. Three Mile Island in 1979 tested that new regulatory structure and, while causing no confirmed public health effects, so thoroughly alarmed the public and utilities that no new commercial reactor construction began in the United States again for thirty years.
On arms control, the record is mixed but real: the Partial Test Ban Treaty, the Non-Proliferation Treaty, START I, and New START each achieved verified, binding reductions or restrictions that previous decades of unilateral restraint never had. New START's expiration on February 5, 2026, after Russia's 2023 suspension, left the American and Russian arsenals without any bilateral numerical limit for the first time in more than fifty years, a development arms control organizations have called a significant and unresolved setback, presented here as a documented current fact rather than a judgment on any government's policy.
Did You Know?
A quick-reference set of facts drawn from the sourced material throughout this page.
- Oak Ridge, Tennessee, alone accounted for 63 percent of the entire Manhattan Project's budget, more than Hanford and Los Alamos combined.
- Most of the Y-12 plant's uranium enrichment machines at Oak Ridge were operated by young women recruited locally, later nicknamed the Calutron Girls, who were never told what the equipment produced.
- The U.S. nuclear stockpile peaked at 31,255 warheads in 1967 and has fallen by roughly 88 percent since, to about 3,700 warheads in the stockpile today.
- The United States has not physically detonated a nuclear weapon in a test since September 23, 1992, relying instead on supercomputer simulation to certify the stockpile.
- It took the National Ignition Facility until December 5, 2022, sixty years after fusion research began, to achieve the first net energy gain from fusion in a laboratory.
- Vogtle Units 3 and 4 in Georgia took fifteen years and $36.8 billion to complete, more than two and a half times their original 2009 cost estimate.
- The Department of Energy does not expect the Hanford Site cleanup to be finished until 2086, with some monitoring continuing until 2100, more than a century after the site stopped making plutonium in 1987.
- Ninety-four commercial reactors at 54 plants supplied about 19 percent of all U.S. electricity in 2024, more than any other single country's nuclear fleet.
- When New START expired on February 5, 2026, it left the U.S. and Russian arsenals without a bilateral numerical limit for the first time since the original SALT talks began in 1969.
Sources & Further Reading
- The Costs of the Manhattan Project, Brookings Institution
- Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons Since 1940, Brookings Institution
- Manhattan Project National Historical Park, U.S. National Park Service
- A History of the Energy Research and Development Administration, U.S. Department of Energy, Office of Legacy Management
- Atomic Fission: The Breakup of the Atomic Energy Commission and the Energy Reorganization Act of 1974, U.S. Nuclear Regulatory Commission
- Backgrounder on the Three Mile Island Accident, U.S. Nuclear Regulatory Commission
- Fifty for 150: FBI Raids the Rocky Flats Nuclear Weapons Plant in 1989, Colorado Newsline / States Newsroom
- Projected Costs of U.S. Nuclear Forces, 2023 to 2032, Congressional Budget Office
- DOE Report: Cost to Finish Cleaning Up Hanford Site Could Exceed $589 Billion, American Nuclear Society, Nuclear Newswire
- America's Nuclear Weapons Arsenal 2024, Federation of American Scientists
- FY24 Budget Outlook: National Nuclear Security Administration, American Institute of Physics, FYI
- Radiation Exposure Compensation Act, U.S. Department of Justice, Civil Division
- Lawrence Livermore National Laboratory Achieves Fusion Ignition, Lawrence Livermore National Laboratory
- What Was Learned From Building New Nuclear Reactors?, POWER Magazine
- Sentinel ICBM Cost Grows to Nearly $141 Billion, 81% More Than Originally Forecasted, Stars and Stripes
- How Many Nuclear Power Plants Are in the United States, and Where Are They Located?, U.S. Energy Information Administration
- New START at a Glance, Arms Control Association