Before the building of an airfield, Greenham Common was a massive piece of common land. It was used for troop movements during the English Civil War and in the eighteen and nineteenth centuries.
In late 1943, Greenham Common airfield was turned over to the USAAF Ninth Air Force. An American advance party soon arrived to ready the airfield for the incoming units. Greenham Common was known as USAAF Station AAF-486 for security reasons by the USAAF during the war, and it was referred to by this name instead of by location. Its USAAF Station Code was "GC".
The first arrival was the 51st Troop Carrier Wing Headquarters, arriving in September 1942. The 51st TCW controlled the three troop carrier groups at RAF Keevil (62nd TCG), RAF Aldermaston (60th TCG) and RAF Ramsbury (64th TCG) as part of Twelfth Air Force. The Wing Headquarters was located in requisitioned Bowdown House, a mansion on the northeast end of the airfield, and made use of the runways for its communication and courier flights.
The 51st TCW HQ followed its groups to North Africa as part of Operation Torch in November 1942.