At 05:29:45 in the morning on July 16th, 1945, the US Army conducted a test of the first atomic bomb, which had an energy equivalent to 20 kilotons of TNT. Trinity was the code name for the test.
The site chosen was in a remote part of the Alamogordo Bombing Range, now the White Sands Missile Range. The test site was at the northern end of the range, between the towns of Carrizozo and Socorro, New Mexico, in the Jornada del Muerto in the southwestern United States. The explosion left a crater of radioactive glass in the desert 10 feet deep and 1,100 feet wide. At the time of detonation, the surrounding mountains were illuminated “brighter than daytime” for one to two seconds, and the heat was reported as “being as hot as an oven” at the base camp located 10 miles southwest of the test site. The roar of the shock wave took 40 seconds to reach the observers. The shock wave was felt over 100 miles away, and the mushroom cloud reached 7.5 miles into the atmosphere.
More than sixty years after the test, residual radiation at the site measured remains ten times higher than normal. The Trinity monument, a rough-sided, lava rock obelisk around 12 feet high, marks the explosion’s hypocenter.
More info:
Trinity (nuclear test) – Wikipedia