The Ojibwe knew this island as Anipich, meaning 'place of the hardwood trees,' and the dense maples that earned that name still define St. Joseph Island today. At roughly 365 square kilometers, it is the third largest island in the Great Lakes, trailing only Manitoulin and Isle Royale. The island sits at the mouth of the St. Marys River where Lake Superior's waters pour toward Lake Huron, a position that made it a strategic midway point for French explorers, Jesuit missionaries, and fur traders traveling between Quebec and the upper lakes. The first European believed to have seen the island was Etienne Brule, whose 1621 voyage took him along the north channel of Lake Huron. By the 1740s, Jesuit missionaries had named it Saint Joseph, and a 1735 French map appears to be the first to record 'Isle St. Joseph.'

When the Jay Treaty forced Britain to surrender Fort Mackinac to the Americans in 1796, officials chose St. Joseph Island as the site for a replacement garrison. Lieutenant Governor John Graves Simcoe argued that maintaining a presence on Lake Huron was essential for relations with First Nations peoples, whose support was critical to defending British North America. The fort was built on the island's southeastern corner, and settlers followed the garrison. But conditions were brutal. The commandant complained that every building leaked in rain and snow. Soldiers deserted, some recovered frozen to death or needing amputations. Fort storekeeper John Askin Jr. described the Ojibwe trading situation in a 1808 letter: the entire hunt of 120 men over several months had produced just five beaver skins, twenty martens, and eight fox skins. When the War of 1812 began, this struggling outpost launched the surprise attack on Mackinac that became Britain's first victory in the conflict.

After the war, St. Joseph Island lay virtually uninhabited until Major William Kingdom Rains purchased over 2,200 hectares in 1834 to establish a colony he named Milford Haven, after a seaside resort near his Welsh hometown. The colony struggled, but settlement picked up when the Free Grants and Homestead Act of 1868 drew farmers from southern Ontario with the promise of 200 acres per household. John Richards founded Richards Landing in 1876, and John Marks established what became Hilton Beach two years later. The sugar maples that blanketed the island supported what grew into Ontario's largest maple syrup industry, with nearly 30 producers now generating 18 percent of the province's output. In 1900, Chicago merchant Edward H. Pitkin purchased nearby Sapper Island and hired his neighbor Frank Lloyd Wright, then a young architect, to design a cottage. Completed in 1902, the 130-square-meter Pitkin Cottage is the only surviving building Wright designed in Canada.

Until 1972, the only way to reach St. Joseph Island was by water. Cable ferries connected the island to the mainland starting in 1919, and a government diesel ferry called the St. Joseph Islander ran from Humbug Point beginning in 1953. When the bridge was finally built, it was named in 1994 for Bernt Gilbertson, an island resident and member of provincial parliament who had long petitioned for its construction. Today, Ontario Highway 548 loops 70 kilometers around the island, making it a popular cycling route. The permanent population has reached a historic high of 2,320 residents, though summer cottagers swell that number to as many as 10,000. Fort St. Joseph's ruins are now a National Historic Site administered by Parks Canada, where occasional archaeological digs still turn up artifacts. The St. Joseph Island Museum preserves buildings spanning two centuries, including a log school from 1877 and the original Kentvale general store. Every April, the island's maple syrup festival draws thousands, keeping alive a tradition rooted in the same hardwood forests the Ojibwe named this place for.