The Manhattan Project's Y-12 plant in Oak Ridge, Tennessee, was a city built from scratch and kept secret from most of the world. Here, thousands of young women, recruited straight from high school, were trained to operate the incredibly complex and delicate calutrons. These machines, based on Ernest Lawrence's invention, used electromagnetic separation to isolate the rare uranium-235 isotope needed for an atomic bomb—a task so difficult even experienced scientists struggled with it. In a now-fa