Rock Island Arsenal occupies a 946-acre island in the Mississippi between Davenport and Rock Island and combines deep historical significance with an ongoing military role. Used for thousands of years and long valued by the Sauk as a summer place, it became a U.S. military reservation in 1809, with Fort Armstrong built in 1816 and later serving in the Black Hawk War. During the Civil War, part of the island held more than 12,400 Confederate prisoners under harsh conditions. After the war it developed into a major ordnance manufacturing center and remains the nation’s largest government-owned weapons manufacturing arsenal, with historic buildings, cemeteries, and military institutions reflecting its layered past.