The McDonald Ranch House, also known as Trinity Site, in the Oscura Mountains of Socorro County, New Mexico, was the location of assembly of the world's first nuclear weapon. The active components of the Trinity test "gadget", a plutonium Fat Man-type bomb similar to that later dropped on Nagasaki, Japan, were assembled there on July 13, 1945. The completed bomb was winched up the test tower the following day and detonated on July 16, 1945 as the Trinity nuclear test.