Constituted 3 May 1861 in the Regular Army as Company A, 1st Battalion, 12th Infantry.
20 October 1861 at Fort Hamilton, New York.
Reorganized and re designated 7 December 1866 as Company A, 12th Infantry.
12th Infantry assigned 17 December 1917 to the 8th Division.
15 August 1927 from assignment to the 8th Division and assigned
to the 4th Division.
October 1933 from assignment to the 4th Division and assigned
to the 8th Division.
10 October 1942 from assignment to the 8th Division and
assigned to the 4th Division (later re designated as the 4th Infantry Division).
Inactivated 15 July 1947 at Fort Ord, California.
and re designated 1 April 1957 as Headquarters and Headquarters Company, 1st BattleGroup, 12th Infantry and remained assigned to the 4th Infantry Division. (Organic elements concurrently
constituted and activated).
and re designated 1 October 1963 as the 1st Battalion.