The Midwest City Douglas Aircraft Company Plant, designed by The Austin Company in a modern style and built between 1942 and 1943, became a major World War II aircraft production center, manufacturing more than half of the 10,000 C-47 Skytrain U.S. Army cargo planes built during the war as well as C-54 Skymaster Big Brother transport planes and A-26 Invader bombers. At peak production, at least 38,000 Oklahomans worked there, and more than half were women. After World War II, production ceased and the facility was taken over by what was then Tinker Field. The plant complex is now a historic district that includes several significant buildings. Building 3001, the Douglas Assembly Building, was built for wartime cargo aircraft production between East Drive and the main north/south runway; it is windowless, artificially lit, air-conditioned, designed to emit no light at night in case of bombing, and at approximately 3374 feet by 926 feet is the largest building in Oklahoma. After annexation by Tinker Field, it was adapted for aircraft modification work and later hosted work on AT-6, B-29, B-36, B-50, F-4, and KC-135 aircraft; today it supports aircraft overhaul, engine overhaul, and aircraft parts repair. Building 3113, the Woodworking Mill, built in 1943, originally supplied wooden airplane parts for Building 3001 and now houses the calibration organization for the Precision Measurement Equipment Laboratory. Building 3303, the Pump House on Staff Drive, built in 1943, pumped water to storage tanks used to cool transformers and remains in use. Building 3202, the Fire Pump Station at Staff Drive and Turbine Drive, has continuously served as a water pumping facility since 1943, providing fire protection for the surrounding area and for the wartime plant complex. Building 3203, the Fire Protection Water Storage Tank, designed by Turnbull, Sverdrup, and Parcel Consulting Engineers and built in 1943, is a partially subterranean, earthen-bermed circular tank 70 feet in diameter and about 20 feet deep that holds 475,000 gallons, with only its upper three feet visible above ground, and it continues in the same role. Building 3105, the Paint Building, constructed in 1943 west of Building 3001, was used to paint assembled aircraft during World War II and later became a maintenance hangar after construction of Building 2280, the Paint Hangar.