Throughout the 1930s, airplanes were generally built one at a time, which limited output. Automobiles, however, were mass-produced on assembly lines, and when war came, the nation turned to car manufacturers to help speed up the process.

In 1940, with Europe embroiled in war, President Franklin Delano Roosevelt requested that “this nation [gear] up to the ability to turn out at least 50,000 planes a year,” and asked Congress for a significant increase in defense spending. The National Defense Advisory Committee determined that massive expansion of factory space and workforce would be essential to achieve this goal.

Among the visionaries on the committee was auto industry executive William Knudsen, whose challenge was to apply assembly line techniques to aircraft building. The committee decided that new plants should be constructed in middle America. Multiple cities were selected so that housing, transportation, and other urban infrastructures would not be overwhelmed. The Kansas City plant would be located at an existing airport on the banks of the Missouri River, in the Fairfax industrial district. It would be funded and built by the government, but would be operated under the name North American Aviation, Inc., of Kansas, which was sometimes abbreviated to NAA-K.

Consistent with aircraft plants then under construction, the Kansas City plant was built of steel and concrete without windows so work could continue in blackout conditions, making it necessary to air-condition the massive building. Constant temperature would minimize expansion and contraction of metal, ensuring a better fit.

In four short years, it was over. B-25 production was abruptly halted on August 17, 1945, when it became evident that the capitulation of the Japanese was imminent. In November 1945, the official North American Aviation, Inc. of Kansas workforce would number zero. On December 1, 1945, General Motors took occupancy of the vacated plant. The first automobile rolled off the line in June 1946.

Browse the gallery, above, to see images from the wartime B-25 factory.

Text and images adapted with permission from Kansas City B-25 Factory, by John Fredrickson and John Roper. Available from the publisher online, or by calling 888-313-2665.