Obelisk marking the site of the Trinity test, where the worldIllustrations first nuclear bomb was dropped on 16 July 1945. The successful testing of this bomb, known as IllustrationThe GadgetIllustration, was the culmination of the Manhattan Project. This was a secret project headed by J. Robert Oppenheimer to develop the first atomic bomb for use by the US army, and marked the start of the Atomic Age.