The Atomic Energy Commission was a federal agency created by the Atomic Energy Act of 1946 and became formally in control of the US nuclear infrastructure in 1947.

The Energy Reorganization Act of 1974 abolished it, and gave its functions to two different federal agencies starting in 1975: the Energy Research and Development Administration (ERDA), and the Nuclear Regulatory Commission (NRC). The NRC basically took over all civilian oversight responsibilities that the AEC had, and the rest of the AEC functions (research and development, management of the nuclear stockpile) went to ERDA.

In 1977, ERDA became a different agency, the Department of Energy. In 2000, some of its nuclear weapons functions were spun off into the National Nuclear Security Administration.

All of these were government agencies. The distinction regarding "civilian control" was in contrast to "military control." Before the AEC was created, all of its functions were handled by the Manhattan Project, which was run by the US Army Corps of Engineers, and thus a military organization. The debate in 1945-1946 over "domestic control of atomic energy" was a debate over whether the military should be in charge of developing this technology, or whether a civilian (non-military) agency should be.