Who was the first to make an atomic bomb?

The US developed the first nuclear fission weapons (atomic bombs) during World War II as part of the Manhattan Project, a top-secret military program that saw several firsts in nuclear chain reaction experiments. Through the work of many international physicists and other experts, the US exploded the first a-bomb near Alamogordo, New Mexico on July 16, 1945.

The following two bombs were used in August, 1945, against the Empire of Japan, destroying the cities of Hiroshima and Nagasaki.