The Manhattan Project was the United States project, conducted primarily during World War II, to develop a nuclear weapon. It was commanded by Major General Leslie Groves, with J. Robert Oppenheimer as technical director. Set up in 1942, the project came to a head with the detonation of the first fission device, the Trinity test, in 1945 at White Sands, New Mexico.
Major facilities included:
- "Site Y" in New Mexico, the actual bomb laboratory, now the Los Alamos National Laboratory
- Gaseous diffusion plant for uranium in Tennessee, now the Oak Ridge National Laboratory
- Hanford Plant, in Washington, now closed but the major plutonium production facility
- "Metallurgical Laboratory" at the University of Chicago, the first nuclear reactor