The Trinity test, as it was known, was the culmination of the American effort to win the race against Germany (and, ultimately, the Soviet Union) in building an atomic bomb. A mere three weeks after the test, the United States used atomic bombs to destroy the Japanese cities of Hiroshima and Nagasaki.
But prior to the 16th, none of those involved in the project knew if they had built a devastating new weapon or a spectacular dud.
Even those who designed the bomb were moved by its performance. J. Robert Oppenheimer famously quoted the Bhagavad Gita:
"If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendor of the mighty one. Now I am become Death, destroyer of worlds."
More prosaically, Dr. Kenneth Bainbridge, site director of the Trinity test, said: "Now we are all sons-of-bitches."
Wired has the story and a photo gallery. Link