Trinity was the code name of the first detonation of a nuclear weapon, conducted by the United States Army on July 16, 1945, as a result of the Manhattan Project. The new test site, named the White Sands Proving Ground, was built in the Jornada del Muerto desert about 35 miles (56 km) southeast of Socorro, New Mexico, at the Alamogordo Bombing and Gunnery Range (now part of the White Sands Missile Range).
Trinity used an implosion-design plutonium device, informally nicknamed “The Gadget”. Using the same conceptual design, the Fat Man device was detonated over Nagasaki, Japan, on August 9, 1945. The Trinity detonation produced the explosive power of about 20 kilotons of TNT (84 TJ).
Although nuclear chain reactions had been hypothesized in 1933 and the first artificial self-sustaining nuclear chain reaction (Chicago Pile-1 or CP-1) had taken place in December 1942, the date of the Trinity test is usually considered to be the beginning of the Atomic Age.