First Army is the oldest and longest-established field army of the United States Army. It served as a theater army, having seen service in both World War I and World War II, and supplied the US Army with Soldiers and equipment during the Korean War and the Vietnam war under some of the most famous and distinguished officers of the U.S. Army. It now serves as a mobilization, readiness and training command. First Army partners with the Army National Guard and the US Army reserve, to enable Reserve Component formations to achieve HQDA directed readiness goals and deliver trained and ready RC units.

Location:  

The United States First Army Headquarters is located at Rock Island Arsenal, IL.  Arsenal Island is a 946-acre island in the Mississippi River that is centrally located within the Illinois and Iowa bi-state metropolitan area known as the Quad Cities.  The Quad Cities consists of Davenport, IA; Bettendorf, IA; Rock Island, IL; Moline and East Moline, IL.

Division East is at Fort Knox, KY, and Division West at Fort Hood, TX, with ten geographically dispersed brigades throughout the United States.

First Army has operational control of the 85th Army Reserve Support Command, headquartered at Arlington Heights, IL.