The Liberty engine was America's most important contribution to aeronautical technology during World War I. Jesse G. Vincent of Packard and Elbert J. Hall of Hall-Scott co-designed it between May 30 and June 4, 1917 for the U.S. government, which wanted a standard design in 4-, 6-, 8-, and 12-cylinder versions that could be quickly mass-produced to equip U.S. combat aircraft. To ensure a workable engine in the shortest possible time, they used only proven components, with features from both Hall-Scott and Packard. They succeeded, with the first 8-cylinder engine delivered in early July.

However, demand for lower-power engines was already being met, and wartime experience showed the need for high power. Liberty-12s powered many aircraft types, but most were built for the de Havilland DH-4. Automakers Ford, Lincoln, Packard, Marmon, and Buick produced 20,748 Liberty 12s, with varying quality, before the Armistice, which insured their widespread use into the 1920s and '30s.