Manhattan Project

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.

It then built the Little Boy used at Hiroshima and the Fat Man bombs used on Nagasaki, on, respectively, August 6 and August 9, 1945.

Major facilities included:

• "Site Y" in New Mexico, the actual bomb laboratory, now Los Alamos National Laboratory
• Gaseous diffusion plant for uranium in Tennessee, now 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