Trinity was the code name of the first detonation of a nuclear weapon, conducted by the United States Army on July 16, 1945, as part of the Manhattan Project. The White Sands Proving Ground, where the test was conducted, was in the Jornada del Muerto desert about 35 miles (56 km) southeast of Socorro, New Mexico, on the Alamogordo Bombing and Gunnery Range. The only structures originally in the vicinity were the McDonald Ranch House and its ancillary buildings, which scientists used as a laboratory for testing bomb components. A base camp was constructed, and there were 425 people present on the weekend of the test.
The code name “Trinity” was assigned by J. Robert Oppenheimer, the director of the Los Alamos Laboratory, after a poem by John Donne. The test used an implosion-design plutonium device, informally nicknamed “The Gadget”, of the same design as the Fat Man bomb later detonated over Nagasaki, Japan, on August 9, 1945. The complexity of the design required a major effort from the Los Alamos Laboratory, and concerns about whether it would work led to a decision to conduct the first nuclear test.
Fears of a fizzle led to the construction of a steel containment vessel called Jumbo that could contain the plutonium, allowing it to be recovered, but Jumbo was not used. A rehearsal was held on May 7, 1945, in which 108 long tons (110 t) of high explosive spiked with radioactive isotopes were detonated. The Gadget’s detonation released the explosive energy of about 20 kilotons of TNT (84 TJ). Observers included Vannevar Bush, James Chadwick, James Conant, Thomas Farrell, Enrico Fermi, Leslie Groves, Robert Oppenheimer and Richard Tolman.