Constituted 3 March 1855 in the Regular Army as Company D, 9th Infantry

Organized 17 March 1855 at Fort Monroe, Virginia

Consolidated in June 1869 with Company D, 27th Infantry (see ANNEX), and consolidated unit designated as Company D, 9th Infantry

(9th Infantry assigned 22 September 1917 to the 2d Division [later redesignated as the 2d Infantry Division])

Inactivated 20 June 1957 at Ladd Air Force Base, Alaska, and relieved from assignment to the 2d Infantry Division; concurrently redesignated as Headquarters and Headquarters Company, 4th Battle Group, 9th Infantry

Activated 25 January 1963 at Fort Wainwright, Alaska (organic elements concurrently constituted and activated)

Assigned 20 May 1963 to the 171st Infantry Brigade

Reorganized and redesignated 1 July 1963 as the 4th Battalion, 9th Infantry

Relieved 14 January 1966 from assignment to the 171st Infantry Brigade and assigned to the 25th Infantry Division

Inactivated 5 June 1972 at Schofield Barracks, Hawaii

Relieved 2 August 1972 from assignment to the 25th Infantry Division, assigned to the 172d Infantry Brigade, and activated at Fort Wainwright, Alaska

Inactivated 6 January 1983 at Fort Wainwright, Alaska, and relieved from assignment to the 172d Infantry Brigade

Assigned 29 April 1983 to the 7th Infantry Division and activated at Fort Ord, California

Relieved 16 April 1987 from assignment to the 7th Infantry Division and assigned to the 6th Infantry Division

Inactivated 15 December 1995 at Fort Wainwright, Alaska, and relieved from assignment to the 6th Infantry Division

Reactivated June 1, 2006 at Ft. Lewis, Washington