The use of atomic bombs on Hiroshima (August 6, 1945) and Nagasaki (August 9, 1945) created the atomic age. A legacy of World War II, nuclear energy was seen both as a threat that might destroy the world and as a new source of energy to advance civilization. Throughout the Cold War (1946–1991) the fear of nuclear holocaust—fed by the arms race with the Soviet Union—and the promise of harnessing atomic power for peaceful uses helped to shape American culture and society. In an attempt to control the destructive side of nuclear power while utilizing its potential for civilian applications, Congress passed the Atomic Energy Act (AEA) of 1946.

The Manhattan Project, which created the atomic bombs used in World War II, had been under military command. The AEA was created in the early stages of the Cold War and the U.S. government's first priority was maintaining...