Constituted 5 August 1917 as the 91st Division.
Organized 26 August 1917 at Camp Lewis, Washington.
Inactivated 13 May 1919 at the Presidio of San Francisco, California.
Activated 7 October 1921 with headquarters at San Francisco, California.
Ordered into active military service 15 August 1942 and reorganized at Camp White, Oregon as the 91st Infantry Division.
Inactivated 1 December 1945 at Camp Rucker, Alabama.
Activated 31 December 1946 with headquarters at San Francisco, California.
Major General William G. Livesey - Assumed command July 1943
Headquarters, 91st Infantry Division
Headquarters Company, 91st Infantry Division
91st Cavalry Reconnaissance Troop
316th Engineer Combat Battalion
361st Infantry Regiment
362nd Infantry Regiment
363rd Infantry Regiment
Headquarters and Headquarters Battery, Division Artillery
346th Field Artillery Battalion
347th Field Artillery Battalion
348th Field Artillery Battalion
916th Field Artillery Battalion
Headquarters, Special Troops
316th Medical Battalion
791st Ordnance Light Maintenance Company
91st Signal Company
91st Quartermaster Company
Rome- Arno, North Apennines, Po Valley