Constituted 18 July 1917 as the 40th Division.
Organized 25 August 1817 at Camp Kearney, California.
Inactivated 20 April 1919 at Camp Kearney, California.
Activated 18 June 1926 with headquarters at Berkley, California.
Ordered into federal service 3 March 1941 at Los Angeles, California.
Reorganized and redesignated 18 February 1942 as the 40th Infantry Division.
Inactivated 7 April 1946 at Camp Stoneman, California.
Activated 14 October 1946 with headquarters at Los Angeles, California.
Major General Rapp Brush - Assumed command April 1942
Major General Donald J. Myers - Assumed command July 1945
Headquarters, 40th Infantry Division
Headquarters Company, 40th Infantry Division
40th Cavalry Reconnaissance Troop
115th Engineer Combat Battalion
108th Infantry Regiment
160th Infantry Regiment
185th Infantry Regiment
Headquarters and Headquarters Battery, Division Artillery
143rd Field Artillery Battalion
164th Field Artillery Battalion
213th Field Artillery Battalion
222nd Field Artillery Battalion
Headquarters, Special Troops
115th Medical Battalion
740th Ordnance Light Maintenance Company
40th Signal Company
40th Quartermaster Company
Bismarck Archipelago, Luzon (with arrowhead), Southern Philippines