The Calutron Girls of Oak Ridge

They were young women from rural Tennessee and the surrounding states, most of them recent high school graduates, and they had been told very little about the job. The pay was good by wartime standards. The work was steady. Their supervisors were engineers who gave them precise instructions: watch these needles, turn these dials when the reading drifts above this line, call for maintenance if the pressure drops below this threshold.

No one told them what they were producing. That was by design.

The facility was called Y Twelve, one of several enormous plants that had been constructed in less than two years on fifty-nine thousand acres of east Tennessee farmland the Army had purchased and cleared, displacing about one thousand farming families, some with only a couple of weeks' notice. Oak Ridge, which did not appear on any public map until the war was over, had grown from nothing to a city of seventy-five thousand people, the fifth-largest in Tennessee, and most of its residents did not know what the city was for.

The women at Y Twelve were operating calutrons: electromagnetic separation devices designed by physicists at the University of California. What the calutrons produced, one cycle at a time, was enriched uranium. Their supervisors had noticed that trained physicists kept trying to understand the machines, to optimize them, to ask questions. The young women from Tennessee simply did what they were told. They followed the needles. That reliability was considered a security advantage.

The uranium their hands helped separate, accumulated over months of dial-turning in a building the size of several city blocks, became the core of the weapon dropped on Hiroshima, Japan, on August sixth, nineteen forty-five. When the news reached Oak Ridge by radio, some of the women reported that they had felt something that was neither simply pride nor simply horror, but a combination of both that had no good name.

Their role in the history of the Manhattan Project was classified for years and remains underrepresented in the popular account of the war. Their names appear in institutional histories at Oak Ridge National Laboratory and in features published by the Smithsonian Institution. They were not scientists. They were instrument readers. They did not know what they were building until the world heard about it the same moment they did.