Chicago Pile-1 and the first nuclear chain reaction

In a rackets court beneath the west stands of the University of Chicago's Stagg Field, Enrico Fermi's team stacked graphite blocks and uranium into a pile and, on the afternoon of 2 December 1942, achieved the first human-made self-sustaining nuclear chain reaction. The Manhattan Project's Metallurgical Laboratory built on it to design the reactors that produced plutonium for the first atomic bombs.