The code name for the secret project to develop the atomic bomb in the USA during World War II. When it became apparent in the late 1930s that it was feasible to build such a bomb Albert Einstein was persuaded by the physicist Leo Szilard to write to President Roosevelt, urging him to provide the resources to enable the USA, rather than Germany, to develop the atom bomb. Largely as a result of this initiative work was started on designing such a weapon at Los Alamos, New Mexico, under the direction of Oppenheimer, who had the collaboration of the University of Chicago, where Enrico Fermi (1901–54) built the first atomic pile. Also involved were other physicists in US and UK universities. Uranium-235 was produced at Oak Ridge, Tennessee, and plutonium-239 at an atomic plant at Hanford, Washington state. The project culminated in the successful explosion of the first atomic bomb at Alamogordo, New Mexico, on 16 July 1945. After the war it became clear that the Germans, who had lost their mainly Jewish nuclear physicists, were many years behind the Americans.