The Wikipedia article of the day for July 16, 2017 is Project Y.
The Los Alamos Laboratory was a secret laboratory in a remote part of New Mexico established by the Manhattan Project during World War II and operated by the University of California. Its mission was to design and build the first atomic bombs. The laboratory was designing a plutonium gun-type fission weapon called Thin Man until April 1944, when it determined that the nuclear reactor-bred plutonium in the bomb could predetonate before the core was fully assembled. Robert Oppenheimer reorganized the laboratory, and orchestrated an all-out effort on an alternative design, an implosion-type nuclear weapon called Fat Man. The gun-type Little Boy was developed using uranium-235. The laboratory also built an aqueous homogeneous reactor, and researched the hydrogen bomb. The Fat Man design was used in the Trinity nuclear test on 16 July 1945, and laboratory personnel participated in the bombing of Hiroshima and Nagasaki as pit crews, weaponeers and observers. Oppenheimer was succeeded as director by Norris Bradbury in December 1945. After the war, assembly activities moved to Sandia. The Los Alamos Laboratory became the Los Alamos Scientific Laboratory in 1947.