The 556th Signal Company was constituted on 3 February 1944 in the Army of the United States as the 556th Signal Depot Company and activated on 1 April 1944 at Camp Polk, Louisiana. During WWII the 556th served in Hawaii and on Saipan Island returning to Hawaii in 1946 where it was inactivated on 31 October 1946. For its WWII service the company was awarded a Meritorious Unit Commendation.
Redesignated as the 556th Signal Radio Relay Company it was reactivated in Korea on 10 November 1951 and assigned to the Eighth Army. The company served in four campaigns of the Korean War receiving two Meritorious Unit Commendations before being inactivated on 12 March 1953 in Korea. Redesignated as the 556th Signal Company, it was reactivated in Korea from 15 March 1960 to 15 December 1962 as a radio relay company assigned to the Eighth Army.
On 1 March 1970 the 556th Signal Company (Support) was reactivated in Vietnam. Stationed at Dalat, the company was assigned to the U.S. Army Strategic Communications Command and participated in five Vietnam campaigns before being inactivated on 26 January 1972 in Vietnam.
The 556th later served on active duty at Fort Huachuca, Arizona from 16 April 1993 to 15 September 1998 where it received an Army Superior Unit Award. On 16 October 2005 the 556th Signal Company was officially reactivated and assigned to the 2nd Brigade Combat Team (Stryker), 25th Infantry Division at Schofield Barracks, Hawaii.
World War II: Asiatic-Pacific Theater, Streamer without inscription