Frenchman Flat is a hydrographic basin in the Nevada National Security Site south of Yucca Flat and north of Mercury, Nevada. The flat was used as an and has a dry lake bed (Frenchman Lake) that was used as a 1950s airstrip before it was chosen after the start of the Korean War for the Nevada Proving Grounds. Nellis Air Force Base land was transferred to the Atomic Energy Commission on which Site Mercury was constructed on the flat for supporting . The 1951 Operation Ranger "Able" test (ground zero at UTM Coordinates 923758 on the flat) was the first continental US nuclear detonation after the 1945 Trinity test, and Frenchman Flat also had the only detonation of an American artillery-fired nuclear projectile in the 1953 Upshot-Knothole Grable test using the M65 Atomic Cannon.