Fort Holmes was a fortified earthen redoubt located on the highest point of Mackinac Island. Originally built in 1814 by British forces during the War of 1812, the redoubt was improved by that army throughout the course of the war (1812–1814) to help defend the adjacent Fort Mackinac from a possible attack by the U.S. Army.
The British named the redoubt Fort George and reinforced it with cannon, a blockhouse, and a magazine for gunpowder and other munitions. However, Fort Holmes never functioned as an independent military fortification. It was always a dependent outpost of nearby Fort Mackinac.
When United States armed forces reoccupied Mackinac Island in 1815 under the terms of the Treaty of Ghent, they took possession of Fort George. They surveyed and measured their prize, which they renamed Fort Holmes, in honor of Major Andrew Holmes, a casualty in the 1814 Battle of Mackinac Island. However, the American army soon abandoned Fort Holmes. The earthworks and buildings of the former redoubt slowly eroded and disappeared over the course of more than a century.
In 1936, as part of efforts to fight the nationwide Great Depression, a corps of CCC workers were assigned to Mackinac Island. Using the original 1817 American survey and plans, they rebuilt Fort Holmes to its War of 1812 appearance.
As of 2010 most of the reconstructed buildings of Fort Holmes have again disappeared, except for the timbered gateway to the interior of the redoubt. The redoubt's earthen walls also survive. Many visitors come to the fort site for a view of the Straits of Mackinac, much of which is visible from this lookout point approximately 310 feet above the surface of Lake Huron.
In July of 2013 the Mackinac Island State Park announced plans for a second reconstruction of Fort Holmes. The rebuilt redoubt will resume the appearance that it had in 1817.