Manhattan Project

Wartime Organization of Atomic Research

Government involvement with nuclear research began in October 1939, when the financier Alexander Sachs persuaded President Franklin D. Roosevelt that the Germans might be planning an atomic bomb. Sachs delivered a letter to the president that had been signed by Albert Einstein and drafted by the Hungarian physicist Leo Szilard. Szilard and colleagues at Columbia University had recently demonstrated that when a uranium atom was split by bombardment with neutrons, it produced more neutrons. If enough uranium was present, this could, in principle, lead to a self-sustaining chain reaction, releasing large quantities of energy relative to the amount of uranium. The findings [Page 458]confirmed Szilard's longstanding fears that fission of uranium could be used to make an exceptionally powerful bomb. In the letter to Roosevelt, he pointed out that Germany had halted all sales of uranium. Roosevelt agreed to the formation of an Advisory Committee on Uranium, later known as Section-1 or S-1. The committee would oversee Allied research into the feasibility and possible manufacture of atomic weapons.

By the time the United States entered the war at the end of 1941, S-1 had oversight of 16 separate research projects with a total budget of $300,000. The findings indicated that both U235, an isotope of uranium, and the newly discovered element plutonium could be used as the basis of a bomb. By June 1942, laboratory methods of producing these two substances were ready to be scaled up to provide the quantities required for manufacture of a bomb. The project was now brought fully under military control as a new district within the Army Corps of Engineers, designated the Manhattan Engineer District after the Manhattan headquarters of its first director.

In September 1942, Brigadier General Leslie Groves was appointed to lead the Manhattan District. Groves's previous assignment had been managing the construction of the Pentagon. Working with a number of industrial contractors, he now set about building extensive nuclear research and production facilities at three isolated locations: Oak Ridge, Tennessee; Hanford, Washington; and Los Alamos, New Mexico. In addition to research laboratories and some of the world's largest industrial plants, all three sites included new towns to house workers and their families. By the end of the war, Oak Ridge was home to some 75,000 people.

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