First visited (1615–22) by the French Canadian explorer Étienne Brûlé (Brûlé, Étienne), the rapids (in French sault or saut) and river were named for the Virgin Mary, patron saint of the early French missionaries. Jacques Marquette (Marquette, Jacques) founded a mission there in 1668, and the French took possession of the North American interior in a ceremony at the rapids in 1671. The British occupied the area from 1762, and though it had been formally ceded to the United States by the Peace of Paris (Paris, Peace of) in 1783, the British did not completely withdraw from the area until after the War of 1812 (1812, War of). The Treaty of Sault Sainte Marie, negotiated by Michigan territorial governor Lewis Cass (Cass, Lewis) with the pro-British Ojibwa (Chippewa) Indians in 1820, secured for the United States the right to build a fort overlooking the rapids (Fort Brady, 1822) and established the American presence there. With the decline of the fur trade after the 1840s, the locks aided migration and development of the area following the discovery of copper and iron deposits in the Lake Superior region.

Lake Superior State University (1946) occupies the former site of New Fort Brady (built 1893 at a different location from the original 1822 fort). The home of Henry Rowe Schoolcraft (Schoolcraft, Henry Rowe), the Indian agent whose writings inspired poet Henry Wadsworth Longfellow (Longfellow, Henry Wadsworth) to compose The Song of Hiawatha, is maintained as a memorial museum. The SS Valley Camp, a decommissioned Great Lakes freighter converted to a maritime history museum and aquarium, is anchored near the locks. Inc. village, 1879; city, 1887. Pop. (2000) 16,542; (2005 est.) 14,318.

city, seat of Algoma district, south-central Ontario, Canada, on the north bank of St. Marys River, between Lakes Superior and Huron, opposite Sault Ste. Marie (Sault Sainte Marie), Mich., U.S. The site was known to French explorers after the explorations of Étienne Brûlé (1622); it was named Sault Ste. Marie (“Rapids of Saint Mary”) in 1669, when a Jesuit mission was established there by the French. As a part of New France, the area was ceded to the British in 1763, and in 1783 the North West Company founded a trading post there and built a small lock (completed in 1797–98) to handle canoes and small boats for trading purposes. The lock was destroyed by U.S. troops in the War of 1812 and rebuilt as a historical site late in the 19th century.

The growth of Sault Ste. Marie has been closely associated with the rapids and the locks and canal around them. The present Canadian lock was built for military purposes in the late 19th century and later widened to its present size: 18.5 feet (5.6 m) deep, 60 feet wide, and 850 feet long. The canal itself is 1.38 miles (2.22 km) long. Cheap transportation and hydroelectrical power led to the city's development as a centre of heavy industry. Chief manufactures include iron and steel, paper and lumber, tar and chemicals, and beer. In addition, the “Soo,” as the city is sometimes called, is a hunting, fishing, and iron-ore mining centre. It is linked to Sault Ste. Marie, Mich., by international rail and highway bridges and to other Canadian cities by the Trans-Canada Highway and by rail lines. Inc. town, 1887; city, 1912. Pop. (2006) 74,948.