St. Marys River (Michigan–Ontario) St. Marys River (Michigan–Ontario) The St. Marys River (), sometimes written as the St. Mary's River, drains Lake Superior, starting at the end of Whitefish Bay and flowing southeast into Lake Huron, with a fall of . For its entire length it is an international border, separating Michigan in the United States from Ontario, Canada. The twin cities of Sault Ste. Marie, Ontario, and Sault Ste. Marie, Michigan are connected across the St. Marys River by the Sault Ste. Marie International Bridge. The St. Marys Rapids are just below the river's exit from Lake Superior and can be bypassed by
Sault Ste. Marie, Michigan Street in Sault Ste. Marie, Ontario. Shipping traffic in the Great Lakes system bypasses the rapids via the American Soo Locks, the world's busiest canal in terms of tonnage passing through it. Smaller recreational and tour boats use the Canadian Sault Ste. Marie Canal. The city's downtown was developed on an island, with the locks to the north and the Sault Ste. Marie Power Canal to the south. The largest ships are long by wide. These are domestic carriers (called "lakers"). Too large to transit the Welland Canal that bypasses Niagara Falls, they are land-locked. Foreign ships (termed "salties") are