The 91st Division was an infantry division of the United States Army that played a significant role during World War I, particularly noted for its involvement in the Meuse-Argonne Offensive. It was composed mainly of troops from California and several western states, showcasing the region's vital contribution to the U.S. military efforts during the war. The division became known as the 'Wild West Division' due to its large number of soldiers who hailed from the American West.