The Manhattan Project at Los Alamos and the Trinity test

In 1943 the US Army set up a secret laboratory on a mesa at Los Alamos, where J. Robert Oppenheimer's scientists designed the first atomic bombs; recruits first reported to an office in Santa Fe. On 16 July 1945 the plutonium device was tested at Trinity in the southern New Mexico desert. Weeks later the weapons were used on Hiroshima and Nagasaki.