In February 1943, the Los Alamos Ranch School, an outdoorsy institution for boys, abruptly closed its doors so the U.S. government could take over the campus. A local poet named Peggy Pond Church, daughter of the school’s founder, later described the “element of extreme haste and mystery” that surrounded the whole operation. As bulldozers arrived on the New Mexico campus, she had her first glimpse of J. Robert Oppenheimer. “Cowboy boots and all,” she wrote, “he hurried in the front door and out the back, peering quickly into the kitchen and bedrooms. I was impressed, even in that brief meeting, by his nervous energy and by the intensity of the blue eyes that seemed to take in everything at a glance, like a bird flying from branch to branch in a deep forest.”

Oppenheimer, then 38, had been tapped to lead a facility that government documents called Project Y. The physicists working there were part of the ultra-secret Manhattan Project, and they had one goal—developing the first nuclear weapon before the Nazis beat them to it.

The effort needed a remote location, but Oppenheimer was especially partial to the Ranch School site. A native of New York City, he hadn’t always strutted around in cowboy boots. But he’d fallen in love with the wilderness near Santa Fe during his teens and 20s. Later, he and his family bought a cabin in the Sangre de Cristo Mountains. They called it Perro Caliente, reportedly because Oppenheimer shouted “Hot dog!” when he found out the cabin was available.

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This article is a selection from the July/August 2023 issue of Smithsonian magazine

PAJARITO CANYON - Battleship Bunker
PAJARITO CANYON This fortified structure, called Battleship Bunker, sheltered scientists during weapons testing in the canyon. Two days before Trinity, the canyon was the site of the Creutz Test—the first full-scale trial of the Fat Man bomb’s explosives without the nuclear core. Minesh Bacrania
SLOTIN BUILDING From the side of the Pond Cabin, a view of the Slotin Building, named for Louis Alexander Slotin, the Canadian physicist who assembled the plutonium core for the Trinity test weapon in July 1945. He died less than a year later, at the age of 35, after an accident at Los Alamos exposed him to a lethal dose of radiation. Minesh Bacrania
RIO GRANDE An aerial photograph of the Rio Grande in White Rock Canyon, New Mexico. The area’s spectacular scenery helped the scientists maintain their calm and clarity as they worked on world-altering problems. Minesh Bacrania

Los Alamos had views of the same mountain range. During the last two years of World War II, between 1,500 and 8,200 scientists and staff members lived on the Ranch School campus and in a quickly constructed nearby town. One of the first to arrive, in March 1943, was Richard Feynman, another New Yorker, who had recently earned his PhD at Princeton University. “The beauty of the scenery, for a person from the East who didn’t travel much, was sensational,” Feynman said later. “There are the great cliffs that you’ve probably seen in pictures. You’d come up from below and be very surprised to see this high mesa.” The nearby houses were still under construction. “We were all jammed in there in bunk beds,” Feynman recalled. Another theoretical physicist and his wife had to pass through Feynman’s bedroom to get to the bathroom.

The town of Los Alamos was soon up and running, but its existence remained secret. All its residents shared the same mailing address: P.O. Box 1663. Many people on the support staff were young military personnel and, sequestered away from the world, they had to create their own entertainment. “Square dancing evolved as a natural Saturday evening activity in that Southwestern setting,” Richard Rhodes wrote in his definitive history, The Making of the Atomic Bomb. “Single men and women sponsored dorm parties fueled with tanks of punch made potent with mixed liquors.”

GUN SITE - interior of research building
GUN SITE The inside of a research building at Gun Site, where scientists designed and planned the ballistics tests they carried out in the canyon. Minesh Bacrania
PAJARITO SITE, POND CABIN Ranch School founder Ashley Pond Jr. built this cabin in 1914 as the office of a private club. Because the canyon was several miles east of the main research area, it was an ideal site for testing that involved radiation. Emilio Segrè, who led plutonium research there, described the canyon as “a most poetic place.” Minesh Bacrania
Pajarito Site - old stove
PAJARITO SITE An old stove inside the Pond cabin, which Segrè’s team used as an office. Calculations made there led Project Y to abandon Thin Man, a gun-type plutonium weapon. Scientists began work on a plutonium weapon that used implosion instead of a gun device. The result, Fat Man, was dropped on Nagasaki. Minesh Bacrania

The married scientists found their own ways to relax. The Oppenheimers rode horses on Sunday mornings. Enrico Fermi, who’d recently built the world’s first nuclear reactor, liked to climb mountains with his colleague Hans Bethe, where they could look out at the world from 12,500 feet. Fermi and Bethe had both been born in Axis countries, Fermi in Italy and Bethe in Germany, but they’d fled their homelands because of antisemitism. (Fermi’s wife was Jewish, and Bethe had Jewish ancestry.)

The scientists’ minds were crammed with physics problems and moral questions. “I had many sleepless nights,” recalled the British physicist James Chadwick in a 1969 interview. “And I had then to start taking sleeping pills. It was the only remedy.”

On July 16, 1945, the breakthroughs at Los Alamos were put to the test in a world-changing experiment called Trinity, a few hours south in the New Mexico desert. At 5:29 a.m., onlookers saw a blinding flash of light. “It blasted; it pounced; it bored its way right through you,” wrote Nobel Prize-winning physicist Isidor Isaac Rabi, who was there that day. “It was a vision which was seen with more than the eye. It was seen to last forever. You would wish it would stop; altogether it lasted about two seconds.” The flash gave way to a massive fireball with streaks of yellow, red and green. “It looked menacing. It seemed to come toward one. A new thing had just been born; a new control; a new understanding of man, which man had acquired over nature.”

V-SITE - candy kettle
V-SITE Access to V-Site was especially limited, as weapons were assembled and tested there. To make explosive lenses—specialized charges whose shape directed the bomb’s energy—scientists heated material in this candy kettle before pouring it into molds. Minesh Bacrania
K-SITE To develop Fat Man, scientists needed a better understanding of implosion—a process that would start a chain reaction by compressing plutonium. From the hole in this bunker, they sent X-rays through an implosion and into another bunker that held measurement equipment. Minesh Bacrania
GUN SITE - bunker
GUN SITE Little Boy, the bomb dropped on Hiroshima, had a gun-type design, which fired one mass of uranium at another to launch a chain reaction. This bunker, built into a canyon, was a safe haven where scientists watched tests above them using a periscope. Minesh Bacrania

A few weeks later, on August 6, Americans dropped the first atom bomb, devastating the Japanese city of Hiroshima. Three days later, another plane dropped an atom bomb on Nagasaki. On the evening of August 14, President Harry S. Truman told reporters at the White House that Japan had surrendered. That was the last time nuclear weapons were used in combat, though their proliferation still causes countless cases of insomnia. The scientists who developed the weapons live on in the public’s imagination, most recently inspiring the Christopher Nolan film Oppenheimer, which opens this summer.

QUONSET HUT - exterior
QUONSET HUT This structure was erected in 1945 to assemble a mock-up of the Fat Man weapon. Because the bomb would be put together in a quonset hut on Tinian Island in the Pacific Ocean, scientists wanted to develop the assembly procedure in a similar environment. Minesh Bacrania
V-SITE - hubbellite floor
V-SITE The high-explosives package for Trinity was assembled at V-Site. Most of the site’s hastily constructed buildings later burned in wildfires. This hubbellite floor is all that remains of one. It’s red because it contains copper, which helped fortify it during explosions. Minesh Bacrania
CONCRETE BOWL The device tested at Trinity would use half the world’s plutonium supply, so scientists tested a method for recovering the material—a 200-foot-wide concrete bowl, filled with water, that would catch bits of plutonium. This method was ultimately abandoned. Minesh Bacrania

Los Alamos is still an active national laboratory, and the Manhattan Project sites are still off limits to the public. Photographer Minesh Bacrania, a physicist who worked in the lab’s nonproliferation division from 2006 to 2012, received special permission to take these photos for Smithsonian of restricted historic sites that are no longer in operation.

“You can trace so many discoveries back to the work done at Los Alamos,” Bacrania says. The Manhattan Project and the Cold War gave rise to innovations like integrated circuits, earth-sensing satellites, new medical imaging techniques and high-performance computing. “That iPhone in your pocket can be traced all the way back to a little shed in a canyon,” he notes.

Still, Los Alamos will always be remembered as the birthplace of the atom bomb. Many would argue that this weapon has secured a kind of peace, as superpowers continue to avoid mutually assured destruction. But the scientists themselves never stopped grappling with what they’d done. “The physicists have known sin,” Oppenheimer said two years after the war, “and this is a knowledge which they cannot lose.”

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