The Manhattan Project refers to the effort to develop the first nuclear weapons during World War II by the United States with assistance from the United Kingdom and Canada. Formally designated as the Manhattan Engineering District (MED), it refers specifically to the period of the project from 1942-1946 under the control of the U.S. Army Corps of Engineers, under the administration of General Leslie R. Groves, with its scientific research directed by the American physicist J. Robert Oppenheimer.
The project succeeded in developing and detonating three nuclear weapons in 1945: a test detonation on July 16 (the Trinity test) near Alamogordo, New Mexico; an enriched uranium bomb code-named "Little Boy" detonated on August 6 over Hiroshima, Japan; and a plutonium bomb code-named "Fat Man" on August 9 over Nagasaki, Japan.
The project's roots lay in scientists' fears since the 1930s that Nazi Germany was also investigating such weapons of its own. Born out of a small research program which began in 1939, the Manhattan Project would eventually employ over 130,000 people and cost a total of nearly $2 billion USD ($20 billion in 2...