Fort Armstrong (1816–1836), was one of a chain of western
frontier defenses which the United States erected after the
War of 1812. It was located at the foot of
Rock Island, Illinois, in the
Mississippi River near the present-day
Quad Cities of Illinois and Iowa. It was five miles from the principal
Sac and Fox village on
Rock River in
Illinois. Of stone and timber construction, 300 feet square, the fort was begun in May 1816 and completed the following year. In 1832 the US Army used it as military headquarters during the
Black Hawk War. It was garrisoned until 1836, usually by two companies of United States regulars.