Fort Mackinac was an American outpost on Mackinac Island, located strategically in the strait between Lake Michigan and Lake Huron, and a crucial waterway for the fur trade. When the United States declared war in June, 1812, the British commander, Isaac Brock, dispatched a voyageur canoe expedition (likely including several Métis) to the British garrison at Fort St. Joseph near Fort Mackinac to instruct Charles Roberts, the British commander there to lead an assault on Fort Mackinac and seize control of the island.

Responding quickly to the orders, on July 17, seventy war canoes and ten other boats manned by Métis, First Nations and British allies left Fort St. Joseph and landed without being detected on the north end of Mackinac Island. There they were able to remove the civilian population and train two cannons on the fort. The American garrison, not even aware that the United States had declared war, was taken entirely by surprise when Captain Roberts demanded their surrender. The Americans, seeing that they were outnumbered, at a strategic disadvantage, and because they were afraid of the First Nations present, surrendered without a shot being fired.

Having captured the fort, it remained in allied hands for the duration of the war and became a base for operations in the area. Consequently, a large number of Métis moved to the island. The Americans tried to re-take it in July, 1814, by attacking with a squadron of five ships carrying a landing force of 700 soldiers. While the Americans succeeded in destroying Fort St. Joseph, they failed to re-capture Mackinac Island, which was ably defended by British soldiers with their Métis and First Nations allies.

The Treaty of Ghent (1814), which ended the War of 1812, gave Mackinac Island back to the Americans, so, with Fort St. Joseph destroyed, the British moved from Mackinac Island and re-located their garrison to Drummond Island with the majority of the Métis population choosing to go with them. Surveys, not completed until 1822, determined that Drummond Island was also part of the United States. Again, the Métis followed the British garrison when it moved, this time to Penetanguishene on the Georgian Bay.