Observers watch the detonation of a nuclear artillery shell in Nevada in 1953

U.S. nuclear testing's devastating legacy lingers, 30 years after moratorium

The United States conducted 1,054 atomic tests—costing more than $100 billion and taking an incalculable toll on humans and the environment.

Witnesses observe the fireball at the Nevada Test Site from the 1953 U.S. nuclear test Grable. The 15-kiloton bomb had about the same explosive power as the device that decimated Hiroshima in 1945.
Photograph via PhotoQuest/Getty

Potassium iodide pills are often given out during nuclear emergencies, actual or imminent. In late August, for example, the European Union pledged to preemptively donate more than five million anti-radiation tablets to Ukraine, amid fears of a Chernobyl-level catastrophe at the Russian-occupied, embattled Zaporizhzhia nuclear power plant.

But for Claudia Peterson, 67, and her peers growing up near Cedar City, Utah, iodide pills were part of their routine—like recess, or homework, or reciting the pledge of allegiance. The ones given to students at her elementary school were big and orange, she recalls.

Another part of the routine: the men in suits who showed up at the school toting Geiger counters. “They would come up to our faces and run this machine over us,” she says. When Peterson asked her teacher what a beeping response from the machine meant, she was told that the device had detected residual radiation from recent dental x-rays. 

“Except,” Peterson says, “I had never had them.”

Formerly an iron mining and agricultural community, Cedar City stands about 175 miles east of the Nevada Test Site, where the United States conducted more than 900 nuclear tests from 1951 through 1992. Others were held across the country, including in Colorado, Alaska, and Mississippi. Tests of the U.S.’s biggest nuclear megaweapons were reserved for sites in the Pacific, including one device in the Marshall Islands a thousand times more powerful than the Hiroshima bomb.

The U.S. carried out its last weapons test on September 23, 1992, with the detonation in Nevada of an approximately 20-kiloton device codenamed Divider. (A kiloton is equivalent to a thousand tons of TNT; the atomic bomb that destroyed Hiroshima was about 15 kilotons.) Just over a week later, on October 2, President George H. W. Bush signed a moratorium on further testing, which has been honored to this day. Now, on the 30th anniversary of that test, National Geographic examines the legacy of U.S. testing in the first half-century of our atomic age.

Before the Nevada tests began, officials told people in Cedar City and other surrounding communities not to worry: There was no danger to anyone beyond the site’s limits, they said. Peterson and her family believed this at first. Yet as fireballs and mushroom clouds kept appearing on the western horizon, it became clear that something was terribly wrong. At a neighboring sheep ranch, “there would be piles of dead lambs,” she says. “Some of them were deformed, with two heads or missing legs.”

Then her schoolmates started getting sick. When she was in sixth grade, she says, a boy one year younger than she died of leukemia. At the same time, another boy around her age got bone cancer and had to have his leg amputated; he died the following year. Just after she graduated from high school, another friend died of liver cancer, Peterson says.

For Peterson and many others, the atomic testing era has never really ended. Many of these “downwinders”—people exposed or likely exposed to radioactive fallout during tests—say that the specter of a possible return to testing someday haunts them. In 2020, when the Washington Post reported that the Trump administration was considering resuming nuclear testing, following unsubstantiated assertions by administration officials that China and Russia were testing low-yield nuclear devices, many in Nevada and Utah decried the decision.

Joe Biden, then a presidential candidate, called the notion “reckless” and “dangerous.” A spokesperson at the National Security Council—chaired now by President Biden—tells National Geographic that “the United States … does not see a need to return to testing” and that the Biden administration calls “on all states possessing nuclear weapons to declare or maintain the zero-yield nuclear explosive testing moratorium.” In the past, Biden has warned that a resumption of U.S. testing might “prompt other countries to resume militarily significant nuclear testing.” 

Experts advise that if a U.S. administration does resume testing, it would risk setting off a new nuclear arms race—as the very first atomic test, in New Mexico, did 77 years ago. During its Cold War nuclear race with the Soviets, the U.S. detonated 1,149 nuclear devices in 1,054 tests—more than those by all seven of the other nuclear-testing nations combined, including the Soviet Union, which conducted more than 700 tests.

In the U.S.’s bid for nuclear supremacy, populations in the vicinity of test sites became collateral damage from radioactive fallout. Officials in charge of the tests also courted environmental and geological catastrophes, including possible earthquakes, tidal waves, dam breaks, and more.

The decision makers “were cavalier by today’s standards,” says nuclear weapons historian Alex Wellerstein. “Today, we say, ‘If you don’t know it’s safe, don’t do it.’ But back then, they leaned toward doing it anyway.” It was a question, he adds, of political priorities. Cold War leaders believed that testing was an existential necessity and that greater harm would come from not testing as the Soviets continued to build their own atomic arsenal.

“The tricky part,” Wellerstein adds, “is that they didn’t give a voice to the people who were going to be at risk.”

The testing program easily cost taxpayers more than $100 billion in fiscal 2023 dollars, according to Stephen Schwartz, nonresident senior fellow at the Bulletin of the Atomic Scientists. Total spending on U.S. nuclear weapons and weapons-related programs “now exceeds $10 trillion and counting,” he says.

The human costs, however, are incalculable.

‘Now, I am become Death’

 In the middle of the night on July 16, 1945, a caravan of buses, cars, and trucks carried about 90 scientists to the Alamogordo Bombing Range—a desert testing ground 125 miles southeast of Albuquerque, New Mexico. Among them was William “Atomic Bill” Laurence, a New York Times reporter conscripted earlier that year as the in-house historian and propagandist of the Manhattan Project. Just before dawn, the team would attempt to detonate an atomic bomb for the first time. 

As some from the group picnicked and passed around “sunburn lotion,” they fretted about whether the years and billions of dollars spent on the top-secret project would work. (Manhattan Project physicists had also deliberated—and placed bets—on whether the bomb might set the Earth’s atmosphere on fire but decided it would be unlikely.)

At 5:30 a.m., the team detonated a 21-kiloton plutonium implosion device nicknamed Gadget atop a hundred-foot tower. The blast—which packed an explosive payload equivalent of about 21,000 tons of TNT—dredged up and irradiated hundreds of tons of soil and sent a mushroom cloud up to 70,000 feet high. For Laurence, the explosion was unlike anything ever seen on the planet: It had the “light of many super-suns” and was “devastating, full of great promise and great forebodings,” he wrote. For physicist and “father of the atomic bomb” J. Robert Oppenheimer, it brought to mind Hindu scripture: “Now, I am become Death, the Destroyer of Worlds.” Everyone there knew, he said later, that “the world would not be the same.”

Some residents of the surrounding areas thought they were witnessing the end of the world. The flash was so bright that a blind girl a hundred miles away saw it, according to one local press report. Within hours, an odd, snow-like ash blanketed the nearby countryside. Fallout was detected as far away as New York State.

None of those living near the Trinity site were warned or evacuated before or after the blast. It had been selected in part for its supposed remoteness from human settlement, but census data from 1940 show that nearly half a million people in New Mexico, Texas, and Mexico lived within 150 miles of ground zero. (Privately acknowledging the “very serious hazard” posed by the blast, the Manhattan Project’s chief medical officer advised that future tests should likely only be conducted where no one lived within a 150-mile radius.) To calm nerves, officials told people that a nearby ammunition dump had exploded. Many learned the truth about the blast only years later, and Trinity test survivors are not among the downwinders eligible for government compensation.

Upon learning of the first successful American nuclear test, the Soviet Union accelerated efforts to develop their own bomb. The Soviets successfully tested their first device in 1949, ending the U.S.’s nuclear monopoly and setting off an international nuclear arms race.

‘Who does this to their own people?’

On January 11, 1951, the U.S. Atomic Energy Commission distributed a handbill to residents of towns and farming communities in southern Nevada and Utah, announcing that it would soon start testing nuclear bombs nearby. Tests would go on indefinitely at what would become known as the Nevada Test Site, 65 miles north of Las Vegas, but there would be no danger to people beyond the perimeter, it said.

Sixteen days later, a B-50 bomber dropped Able, a one-kiloton bomb, over the test site—the first of a hundred aboveground bombs detonated there during the next decade.

For nearby residents, the blasts became a regular occurrence and even, at first, a form of entertainment. And soon, Americans across the country could occasionally experience the bombs voyeuristically on national television, including the 1953 Annie test, whose 16-kiloton blast dramatically incinerated a mock neighborhood dubbed Doom Town, complete with cars and suburban homes filled with furniture and mannequins arranged in various activities. 

Officials assured those living around the site that the detonations were “relatively small in explosive power,” but some blasts were enormous: Hood was a 74-kiloton bomb exploded in 1957 as part of a larger military exercise in a nearby field involving 2,200 U.S. Marines. In 1962, the 104-kiloton Sedan test—seven times as powerful as the Hiroshima bomb—displaced more than 12 million tons of earth and left a hole 1,280 feet wide and 320 feet deep. It has the distinction of being the largest manmade crater in the U.S., and the Nevada Test Site’s Yucca Flat testing region remains the most cratered landscape on the planet, according to the U.S. Department of the Interior.

Tests were conducted on days when winds were projected to blow fallout clouds to the east and northeast—away from Las Vegas, which enjoyed a financial boom from the new nuclear enterprise. Opportunistic business owners turned the detonations into Vegas attractions: Bars concocted atomic-themed cocktails, casinos hosted “dawn parties” at which guests could watch the explosions.

By the late 1950s, enthusiasm for atomic partying was waning fast, as the extent and effects of testing contamination became painfully clear—even as the government attempted to put a positive spin on the situation. In 1955, a U.S. Atomic Energy Commission test manager issued an announcement to those living in communities surrounding the Nevada test site, thanking them for being “active participants” in the program, for their patriotism, and for their stoicism. They’d been exposed to risks from the test flashes, blasts, and fallout but were to be commended for “accept[ing] the inconvenience … without fuss, without alarm, and without panic.” The free world was safer as a result of their sacrifices, they were told.

“We were very trusting, patriotic, family-oriented people,” Claudia Peterson says. “My biggest fear back then was Russia, and what it was going to do to us. Yet it was my own government that was killing my family and my neighbors and my friends. Who does this to their own people?”

Peterson’s father, Ralph Boshell, had a brain tumor the size of a lemon removed and died six months after the operation at age 64, she says. Her sister, Cathy Orton, died of melanoma at 36, leaving behind six children. (She delivered her last baby while she was “full of cancer,” Peterson says.) Peterson’s daughter Bethany was diagnosed with stage 4 neuroblastoma when she was three; she died of acute monoblastic leukemia three years later at age six.

“This testing created a very dangerous environment all across the country,” says Lilly Adams, founder of Nuclear Voices and Senior Outreach Coordinator at the Union of Concerned Scientists. “The Nevada tests created hot spots as far away as Indiana and New York,” she says. Fallout on fields and grazing land led to contaminated milk supplies. “People most at risk were families and especially children who were drinking milk from local farms and dairies.”

Authors of a study published in 1990 in the Journal of the American Medical Association found nearly eight times more leukemia in children under 19 who lived in southwestern Utah during the aboveground testing. Later that decade, a National Cancer Institute study concluded that aboveground testing in Nevada may have produced as many as 212,000 “excess lifetime cases” of thyroid cancer, although Adams says some experts suggested that might be an undercount. Yet another study, conducted jointly in 2005 by the Centers for Disease Control and Prevention and the National Cancer Institute, found that any person living in the contiguous United States since 1951 has been exposed to radioactive fallout from testing.

In 1963, President John F. Kennedy signed a moratorium on atmospheric testing, along with the United Kingdom and Soviet Union. Underground tests were still permissible, however, and the U.S. ultimately conducted 828 at the Nevada Test Site. Although mostly contained underground, radioactive contamination sometimes vented from subterranean detonation caverns.

Conceding at last the consequences to humans of aboveground testing, Congress in 1990 passed the first iteration of the Radiation Exposure Compensation Act for “downwinders” in designated geographic areas suffering as the result of possible exposure to fallout from leukemia, multiple myeloma, lymphomas, or one or more of 16 different cancers.

The act, updated in 2000 and extended earlier this year, has distributed more than $2 billion to downwinders and workers at nuclear sites. Previously ineligible downwinders—including those affected by the Trinity test—are campaigning urgently for inclusion. Claudia Peterson is among those who say the act’s recognition and compensation are insufficient for covering medical costs—and paltry compared to nuclear weapons budgets. “No amount of money can compensate for watching a child die,” she says.

Wellerstein and other experts say that if the U.S. ever does resume nuclear testing, it would likely take place at the former Nevada Testing Site, now renamed the Nevada National Security Site.

Vaporized islands and ‘jellyfish babies’

Tests of the U.S.’s biggest thermonuclear bombs—hugely powerful weapons also known as hydrogen bombs or H-bombs—were reserved for the Pacific Proving Grounds, located largely in the Marshall Islands, some 2,400 miles west of Hawaii. The first U.S. H-bomb—codenamed Ivy Mike, with an explosive payload of 10.4 megatons, nearly 700 times that of the Hiroshima bomb—was detonated in 1952. It vaporized the small island of Elugelab, leaving a crater more than a mile long and 164 feet deep.

Then came Castle Bravo, in 1954, a 15-megaton hydrogen bomb exploded at Bikini Atoll. A bomb that size detonated over New York City would cause up to five million deaths and create a fireball nearly two miles wide, according to NukeMap. (In 1961, the Soviets detonated their largest thermonuclear weapon, the 50-megaton Tsar Bomba, which had “roughly 10 times the total explosive power unleashed in all of World War II, including both the Little Boy and Fat Man bombs that destroyed Hiroshima and Nagasaki,” according to nuclear expert Sara Kutchesfahani.)

“These multimegaton weapons [were] very dirty in terms of their fallout content,” Wellerstein says. Clouds from Ivy Mike and Castle Bravo were closely monitored, he adds, “and they went around the entire world over the course of a week or so.” Contamination spread over roughly 7,000 square miles—“the worst radiological disaster in U.S. history,” according to the Atomic Heritage Foundation.

Fallout landed most heavily on surrounding atolls to the east and southeast of Bikini. Marshallese on Bikini and Enewetak atolls had been relocated before the tests, some to Rongelap Atoll 160 miles away from Bikini. Lijon Eknilang, then an eight-year-old living on Rongelap, witnessed Castle Bravo and in a 2003 testimony recalled the blinding flash and swaying ground. “We were very afraid because we didn’t know what it was,” she said. “The elders said another world war had begun.”

Soon came the telltale cloud, and an hours-long flurry of radioactive debris blanketed Rongelap. Water in containment drums began to change color, “but we drank it anyway, Eknilang said. Then radiation sickness set in: People began vomiting, blistering, and losing hair. Two days later, the U.S. military evacuated 64 Marshallese from Rongelap to a U.S. base on Kwajalein Atoll for medical treatment.

They were allowed to return to Rongelap in 1957 “under continuing radiological surveillance,” according to a 1994 report National Research Council Committee on Radiological Safety in the Marshall Islands. “Later … unanticipated medical problems began to surface,” the report went on.

Eknilang described the illnesses: cancers, leukemias, still births, thyroid tumors, and “jellyfish babies”—infants born without bones and with transparent skin, who usually died within a day or two. Eknilang said she had suffered seven miscarriages and various cancers; she died in 2012. In 1985, the Rongelap people left the island again, relocating to Mejatto Island, on Kwajalein Atoll.

During the late 1970s, the U.S. government built an aboveground, concrete-covered nuclear waste storage site—Runit Dome—about 350 miles away on Runit Island, in Enewetak Atoll. Marshallese call it “the tomb.” The U.S. Department of Energy—successor to the Atomic Energy Commission—oversaw radiological cleanup of Enewetak, done by a workforce of more than 4,000 U.S. servicemen. They loaded the containment unit with more than three million cubic feet (equivalent to 35 Olympic-size swimming pools) of hazardous radioactive test waste; Runit Dome also holds 130 tons of contaminated soil brought from the Nevada Test Site, according to a 2019 Los Angeles Times report. Some veterans who worked on the cleanup say they were unaware that they were working with radioactive materials and were not adequately protected.

Local leaders and experts fear that the dome is threatened by rising seas. In 2015, Tony du Brum—a Castle Bravo survivor and later the foreign minister and minister of health and the environment of the Marshall Islands—called Runit Dome “a cracking concrete crater of nuclear waste slowly leaking into the lagoon—for which my struggling nation has no capacity but has apparently inherited.”

In 2020, however, a Department of Energy report to Congress stated that the “containment structure is still serving its intended purpose” and that “the dome is not in any immediate danger of collapse or failure.” According to the State Department, the U.S. has provided more than $600 million to Marshallese communities affected by nuclear tests.

Blasts on the Ring of Fire

Amchitka Island—near the western end of the Aleutian Island chain, about 1,300 miles west-southwest of Anchorage—sits squarely within the Ring of Fire. This 25,000-mile tectonically active zone along the periphery of the Pacific Ocean is the site of 90 percent of earthquakes and the most violent seismic events recorded on Earth. During the 1960s and early 70s, the U.S. carried out three massive underground tests there. The first, Long Shot, in 1965, was more than five times as powerful as the Hiroshima bomb. The second, Milrow, in 1969, packed more than 10 times the power of Long Shot.

Next came five-megaton Cannikin, a thermonuclear device with an explosive payload 333 times more powerful than the Hiroshima bomb that spurred anger and controversy ahead of its scheduled 1971 detonation. Opponents feared that its subterranean explosion might trigger a major earthquake and calamitous tsunami. Protesters rallied in front of the White House; more than 30 senators called on then President Richard Nixon to halt the test; the Japanese government objected for fear of a tsunami.

“The risks are so great, the gains so dubious, and the debits already so real that the entire experiment appears to be a ghastly and unnecessary mistake,” a New York Times editorial declared.

Atomic Energy Commission officials downplayed the dangers but acknowledged privately that “the worst conceivable effects of Cannikin … cannot be ruled out.” A coalition of environmental groups launched a Hail Mary legal challenge to the test that went up to the Supreme Court. Convening on a day’s notice for a rare Saturday morning session, the court denied the injunction. 

Cannikin—the largest-ever U.S. underground detonation—took place on November 6, 1971, heaving the surrounding earth up some 20 feet and creating a shock equivalent to a 7.0 earthquake on the Richter scale. No seismic disaster followed, but Cannikin was seen as a turning point, igniting citizen outrage over “unchecked freedom with which [atomic] weapons are commissioned, tested, and deployed,” as Time magazine put it at the time.

Radioactive material remains sealed in the test cavities “because no practicable technology exists to remove [it],” according to the Department of Energy, whose Office of Legacy Management continues to monitor seismic activity that might affect the site.

Nuclear fracking

Not all U.S. nuclear detonations were weapons tests; some were intended to find out if nuclear energy and atomic blasts had industrial applications. Gnome, an underground test in 1961 near Carlsbad, New Mexico, was held to determine whether nuclear-blast energy could be converted into electricity. Six years later came Gasbuggy, near Farmington, New Mexico, to explore whether underground atomic detonations could stimulate release of subterranean natural gas. Gasbuggy did release gas, but it was irradiated in the explosion, making it commercially unusable.

Despite this discouraging result, in 1969, the U.S. conducted another nuclear fracking test, near Parachute, Colorado. As with Gasbuggy, radioactivity from the 40-kiloton Rulison explosion contaminated the gas it released, rendering it useless. The next scheduled underground test in Colorado prompted protests and a class action lawsuit filed by a coalition of environmental groups. Yet on May 17, 1973, the Rio Blanco test went ahead anyway, with three simultaneous underground detonations near Meeker. This trio of blasts—also a “natural gas reservoir stimulation” experiment—had a combined explosive payload of 99 kilotons, nearly seven times that of the Hiroshima bomb.

The next year, Coloradans approved a state constitutional amendment requiring voter approval before any atomic detonation could be conducted. The Office of Legacy Management says that the Rulison and Rio Blanco sites are monitored annually for leaked radioactive and hazardous materials, and drilling in the immediate area of the test sites is prohibited. 

‘Everyone’s wells went bad’

After the 1963 moratorium on aboveground nuclear tests, officials began to anticipate the possibility that underground tests also might be banned someday. To determine whether other nuclear powers might be able to carry out covert underground tests, the U.S. started conducting subterranean tests to figure out whether seismic equipment could detect faraway nuclear blasts below ground. 

A subterranean salt dome near Purvis, Mississippi, about 20 miles southwest of Hattiesburg, made an ideal test location—an underground structure that might effectively muffle the sound of an atomic explosion. 

On October 22, 1964, the Atomic Energy Commission and Department of Defense detonated a 5.3-kiloton device dubbed Salmon 2,710 feet down inside the dome. Nearby residents had been evacuated and compensated $10 per adult and $5 per child for the inconvenience. Salmon’s explosion registered 6.0 on the Richter scale and was detected as far away as Sweden; its shockwave lifted the ground four inches and blasted a cavity deep inside the salt dome. Two years later, a smaller nuclear device, Sterling, was detonated in that same space—and this time, the cavity created by the previous blast muffled the explosion, proving that nuclear powers indeed could try to hide tests by detonating atomic devices inside similar underground caverns.

Hundreds of Mississippians in the vicinity reported blast damage, especially from Salmon, to their homes and properties. “Everybody’s wells went bad,” Purvis resident Tom Beshears recalled in a 2014 interview. Public concerns surfaced about health problems possibly related to the tests. In 2000, the U.S. government commissioned a pipeline to bring clean water far from the site so people wouldn’t have to rely on local well water, and in 2015, the federal government paid $16.8 million in settlements to workers employed at the test site or living nearby.

What does the future hold?

Since 1992, the nine nuclear nations largely have honored the testing moratorium. (North Korea remains the exception, having conducted six tests since 2006; India and Pakistan both tested nuclear weapons in 1998.) To date, 186 nations have signed the Comprehensive Nuclear Test Ban Treaty prohibiting any nuclear detonations. The U.S. has not yet ratified it; Russia ratified it in 2000.

The entire U.S. nuclear stockpile is reviewed annually, mainly through “subcritical” tests—blasts that don’t produce a nuclear chain reaction but still test weapon components—and computer simulations. The Stockpile Stewardship Program “has done an amazingly good job,” says Robert Rosner, former chief scientist and director of the Department of Energy’s Argonne National Laboratory.

Yet the possibility that some part of the current testing program might fail, or that a future U.S. administration might resume full-blast testing for political or military reasons, triggers anxiety in testing-era downwinder communities.

“When they talk about reinvigorating the testing program, I want to know: Who is going to accept that in their backyards?” says Tina Cordova, a downwinder activist, cancer survivor, and fifth-generation resident of Tularosa, New Mexico, about 40 miles from the Trinity test site. Generations of her family have now suffered from testing-related cancers and health problems, she says.

“No test is void of risk and danger, and somebody is going to suffer the consequences of that,” she adds. “I just ask: Are you willing to stake your future on that, and the future of your family?”

Lesley M. M. Blume is a journalist, historian, and a New York Times bestselling author, most recently of Fallout: The Hiroshima Cover-up and the Reporter Who Revealed It to the World. This is her third story for National Geographic on the history and legacy of nuclear weapons .

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