Sault Ste. Marie Canals, or Soo Canals, two waterways between Lake Superior -and Lake Huron. The St. Marys River, the natural link between the two lakes, drops some 20 feet (6 m) in shallow rapids near the twin cities of Sault Ste. Marie in Michigan and Ontario. Here the river has been canalized and locks have been built to bypass the rapids and allow ships to sail between the two lakes. One of the canals is on the Michigan side; the other is within Ontario.

The United States canal, properly known as the St. Marys Falls Ship Canal, is just under 2 miles (3.2 km) long and has four locks side by side. Across the rapids is the Sault Ste. Marie Canal, which is 1.4 miles (2.3 km) long and has only one lock. This canal is administered by the Canadian Park Service as a national historic site.

The United States canal is one of the world's busiest waterways. During the eight-month-long shipping season some 10,000 ships pass through the canal. (The canal is closed from mid-December to early April.) Iron ore and wheat are the chief commodities moving out of Lake Superior; coal is the principal inbound cargo.

History

The first canal to bypass the rapids, with a lock for small boats, was built on the Canadian side in the 1790's. It was destroyed by American troops during the War of 1812. Soon after Michigan's admission to the Union in 1837, state leaders urged the building of a canal. After many delays the project was begun by the state, and the first ship canal, with a single lock, was opened in 1855. By permitting easy shipment of the Lake Superior region's vast iron, copper, and lumber resources, the canal played an important part in the industrial development of the United States.

In 1881 a second, larger lock was built by the United States, and the old original lock was replaced in 1896, one year after the present Canadian canal was opened. Additional locks were built in 1914, 1919, and 1943. The 1896 lock was replaced in 1969 with a larger one.