Wikipedia:Today's featured article/July 16, 2015

Trinity was the code name given to the first test detonation of a nuclear weapon. J. Robert Oppenheimer, the director of the Los Alamos Laboratory, took the name from a John Donne poem. It was conducted by the United States Army on July 16, 1945, as part of the Manhattan Project on the Alamogordo Bombing and Gunnery Range in the Jornada del Muerto desert. The only structures originally in the vicinity were on the McDonald Ranch site, 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. It used a Fat Man bomb of the same design as the one that would be detonated over Nagasaki. The complex implosion-type nuclear weapon required a major design effort from the Los Alamos Laboratory, and testing was required to allay fears that it would not work. Its detonation (shown on video) produced the explosive energy of about 20 ktonTNT. The test site is now part of the White Sands Missile Range. It was declared a National Historic Landmark district in 1965, and listed on the National Register of Historic Places the following year.