Fort Mackinac was a military outpost garrisoned from the late 18th century to the late 19th century on Mackinac Island in the U.S. state of Michigan. Built by the British during the American Revolutionary War to control the strategic Straits of Mackinac between Lake Michigan and Lake Huron (and by extension the fur trade on the Great Lakes), it was not relinquished by the British until fifteen years after American independence. It later became the scene of two strategic battles for control of the Great Lakes during the War of 1812. During most of the 19th century, it served as an outpost of the United States Army. Closed in 1895, the fort is now a museum on the grounds of Mackinac Island State Park and has been designated a National Historic Landmark.