St Mary's River

The locks on the St Mary's River at Sault Ste Marie are the hub of navigation on the Great Lakes, neutralizing the 7.2 m (23 ft) drop from Lake Superior to Lake Huron. The first canal to be built at this strategic point was constructed by the North West Company in 1798, but was destroyed in the 1812 war. Next came a lock in 1855, followed in 1895 by a canal on the Canadian side and lock staircase on the American, circumventing the rapids. Today there are five parallel locks of which the 9 m (29 ft) deep McArthur Lock (on the USA side) is the largest.