Frances Dunne was a Swarthmore grad who field-tested mock bomb assemblies as an explosives technician. She was part of the assembly crew for the Trinity test, the world's first nuclear explosion.

Early on the morning of July 16, 1945, the deserts of New Mexico exploded in a colossal, unspeakably brilliant fireball, ushering in the nuclear age at a test site called Trinity. For years, the story of that name remained untold, for good reason.

Robert Oppenheimer, director of the Manhattan Project and its top-secret research site at Los Alamos, New Mexico, named the site Trinity after a poem by John Donne that he had shared with his onetime fiancee, a brilliant psychiatrist (and member of the Communist Party) named Jean Tatlock. She had committed suicide a year earlier. Oppenheimer was married when he named Trinity, by which time he may already have begun an affair with the wife of a fellow scientist.

Oppenheimer’s infidelities were hardly typical, but there was nothing ordinary about family life in Los Alamos, particularly for the women. The women of Los Alamos were enclosed in an extraordinarily secret male enclave in which wives were not allowed to discuss their husbands’ working days, young daughters were submitted to high-security procedures, and female scientists were exceedingly rare.  Reading through scores of oral histories collected by the “Voices of the Manhattan Project” as well as transcripts from congressional hearings and letters among some of the principals offers a unique perspective on the women behind the men who gave us the atomic bomb.   

The Scientists

Perhaps the best known of the women scientists of the Manhattan Project was Maria Goeppert-Mayer, who fled the Nazis in the early 1930s with her husband, chemist Joseph Mayer. She worked for the Manhattan Project in New York City while her husband taught at Columbia University (nepotism rules prevented her also teaching there).  After the war, she worked with Edward Teller on the development of the hydrogen bomb. Her work in nuclear physics would eventually win her the Nobel Prize in Physics for 1963, making her only the second woman to win that prize, after Marie Curie.

Several other women scientists worked at other Manhattan Project facilities around the country—notably Leona Woods Marshall Libby, who worked in Enrico Fermi’s lab at the University of Chicago to demonstrate the first self-sustaining nuclear chain reaction.

Among the few women scientists at Los Alamos, the chemist Lilli Hornig stood out. She and her family fled Nazi Germany and came to the U.S. in 1933. While attending graduate school in chemistry at Harvard, she met her future husband, Don Hornig. Soon after the couple married in 1943, Don Hornig was recruited by the chemist George Kistiakowsky, who was leading efforts at Los Alamos to develop a specialized explosive charge for nuclear weapons. Kistiakowsky assured Lilli that this project would welcome her help because of her chemistry background, but when she met with personnel officials at Los Alamos, they asked how fast she could type.

“I don’t type,” she said.

Eventually, she worked on plutonium chemistry, testing the solubility and the radioactivity of various plutonium salts—a humdrum task, she felt, even if it was a matter of high national security. “It wasn’t terribly inspiring, and nobody actually really spoke with us.”

Concerns that radioactivity could cause reproductive damage in women led to her transfer to the explosives group. After the Trinity test, she joined several of the top Manhattan Project scientists in signing a petition that urged the military to demonstrate the bomb’s destructive capability rather than drop it—or at least before dropping it—on Japan. “We thought in our innocence … if we petitioned hard enough, they may do a demonstration test,” she said. “But of course the military made the decision well before... [that] they were going to use it no matter what.”

The Wives and Daughters

On her mail runs to Santa Fe, twice a day, protected by her gun-toting bodyguard, Adrienne Lowry used to padlock a briefcase to her belt for confidential correspondence. Her husband Joseph, a radiochemist and co-discoverer of plutonium, led the chemistry division at Los Alamos.

Later, military police took over the mail, all of which was censored and routed both ways through an address at the University of California. Los Alamos residents couldn’t tell even their closest relatives where they were. They could not even subscribe to magazines at the UC address because the government didn’t want its scientists’ names appearing on subscription lists. The scientists’ and family members’ driver’s licenses had no names on them, only identifying numbers.

“Many of the women found this [secrecy] very difficult,” said Rose Bethe, whose husband Hans, a future Nobel laureate, headed the theoretical division. That was natural, she said, because before Los Alamos, “the husbands had talked about their work, and it had been a close relationship.”

In the early years at Los Alamos, many young scientists were just starting families, creating a local baby boom so large that General Leslie Groves, who had overall command of the Manhattan Project, said the U.S. Army shouldn’t have to foot the maternity bills.

The Oppenheimers welcomed their daughter Toni in December 1944, in the seven-room hospital at Los Alamos dubbed RFD, for “rural free delivery.” Security procedures required that the birthplace on the birth certificates be marked just “P.O. Box 1663.”

Ellen Bradbury Reid’s childhood games revolved around the secrets of Los Alamos, whether inventing weapons or meeting with spies. She remembered trying to lure lizards into campfires in the hope of turning one into a dinosaur—the ultimate weapon that would keep her father in his job in the high-explosives division. He had mentioned that he was building a bomb, and she was worried about him because bombs had already been invented.

When at last a lizard ran into the fire, she fled to find a ranger. “I was terrified it would work, and I realized it was going to eat my family first!”

The Lovers

In June 1943, not long after Robert Oppenheimer, his wife Kitty, and their toddler son moved to Los Alamos, Oppenheimer flew to San Francisco to visit his old flame Jean Tatlock once more. They had late drinks and dinner, and then he spent the night in her apartment while intelligence officials waited outside—details that would emerge in federal security hearings a decade later that questioned Oppenheimer’s loyalty.

“I wasn’t supposed to say where we were going or anything,” Oppenheimer said, according to transcripts. “I felt that she had to see me. She was undergoing psychiatric treatment. She was extremely unhappy.”

The next morning, she took him to the airport, and he never saw her again. Half a year later, in January 1944, she was found dead in her apartment.

At the 1954 hearings that would eventually deprive Oppenheimer of his security clearance, federal prosecutor Roger Robb asked Oppenheimer why Tatlock had wanted to see him.

“Because she was still in love with me,” he said.

During the war or shortly after, Oppenheimer may have had other romantic entanglements. According to Atomic Love Story: The Extraordinary Women in Robert Oppenheimer’s Life, he adored psychologist Ruth Sherman Tolman, the wife of his close friend chemist Richard Tolman, a scientific adviser to the Manhattan Project. During the war, the Tolmans lived in Washington D.C., where Ruth Tolman worked for the War Production Board and later the Office of Strategic Services, predecessor to the Central Intelligence Agency.

Kai Bird and Martin Sherwin, authors of American Prometheus: The Triumph and Tragedy, contend that Oppenheimer had a “very caring and sweet affair” with Tolman. In their biography, they detail how Ruth Tolman wrote Oppenheimer with a scheme: He could pretend he had to meet someone at UCLA. They’d go away together for the day and return in time for a party that evening.

In another letter, Tolman wrote about their plans for a weekend escape to the beach. “Soon I shall see you. You and I both know how it will be.”

Oppenheimer wrote back, “Ruth, dear heart … I knew that I should find you full of courage and wisdom, but it is one thing to know it, and another to be close.”

Despite all, Oppenheimer and his wife remained together for the rest of their lives. In The Making of the Atomic Bomb, author Richard Rhodes describes Kitty Oppenheimer as a passionate woman who presented herself as someone who needed saving. “Robert jumped in like the white knight that he…wanted to be.”