Formed shortly after the United States declared war on Germany in 1917, the 91st Division (the "Wild West Division") trained for 10 months at Camp Lewis in Washington State before their deployment to France in June 1918. In August of that year, Major General William H. Johnston took over the command of the Division. Their first combat experience was in the area between the Meuse River and Argonne Forest, France, where they distinguished themselves by breaking through the German lines and helping to secure several strong points including Gesnes, Eclis-fontaine, Very, Epinonville, and Tronsol farm. The charge on Gesnes on September 29, 1918, resulted in heavy casualties. The 91st remained in and around Gesnes and Bois de Cierges during the second phase of the battle. Despite their lack of combat experience, the 91st "captured more artillery, machine guns, and prisoners, and advanced a greater distance under fire than many divisions with much longer combat experience." (I-E Section, 3)
On October 16, 1918, the 91st were ordered to fight as part of the armies in Flanders, under King Albert. They traveled by train to Belgium, where they assisted in pushing back the enemy, October 31-November 11. The 91st fought in the Ypres-Lys offensive and captured Audenande, Welden, Petegem, and Kasteelwijk. The Division remained in France and Belgium until the first men sailed for home, January 1919. The Division was demobilized May 14, 1919.