manhattan project
U.S. and British researchers were investigating the feasibility of nuclear weapons as early as 1939. Practical development began in earnest in 1942 when these efforts were transferred to the authority of the U.S. Army and became the Manhattan Project. The weapons-development portion of this project was located at the Los Alamos Laboratory in northern New Mexico, though much other development and production work was carried out at the Clinton Engineer Works near Oak Ridge, Tennessee (the separation of uranium-235); the Hanford Engineer Works near Hanford, Washington.These research, development, and production efforts focused both on the development of the necessary fissile materials to power the nuclear chain reactions in the atomic bombs and on the design, testing, and manufacture of the bombs themselves.