The St. Mary’s River, sometimes written as the St. Marys River, drains Lake Superior starting at the end of Whitefish Bay and flowing 120 km (74.5 miles) southeast into Lake Huron. For its entire length it is an international border, separating Michigan in the United States from Ontario, Canada.
The most important area along the river are the rapids and the twin cities of Sault Ste. Marie (Soo), Ontario and Sault Ste. Marie (Soo), Michigan, with the most famous man-made feature being the Soo Locks. The rapids of the St. Mary's (Sault Sainte Marie in French) are just below the river's exit from Lake Superior.
Two of the Ontario tributaries of this river are the Garden River and the Bar River. Other Canadian tributaries include: Fort Creek, Root River, Little Carp River, Big Carp River, Lower Echo River, Desbarats River, and the Two Tree River. The American tributaries to the St. Mary's River are: Gogomain River, Munuscong River, Little Munuscong River, Brimley River, and the Charlotte River.
Before Europeans arrived, native Americans fished, traded, and maintained a portage around the rapids. French explorer Etienne Brule was the first European to travel up the rapids in about 1621. In 1641, Jesuit priests Isaac Jogues and Charles Raymbault ventured the same route as Brule finding many Ojibwa Indians at the rapids and named it Sault Ste. Marie (sault meaning "rapids" in French).
A set of compensating works (dams w/gates) are located at the mouth of the rapids, which are used to control the outflow of water from Lake Superior. The works consists of 16 gates, half of which are on the American side, and the other half on the Canadian side of the river. They were completed between 1901 and 1921. This flow is controlled by the International Joint Commission.
A concrete berm was constructed along the north side of the rapids as remedial-works to protect fish spawning habitat from lower outflow through the rapids. This was due, in part, by an increase of water outflow from the Francis H. Clergue Generating Station.
Several Islands are encountered by the St. Mary’s River on its way south to Lake Huron. Sugar Island, St. Joseph Island, Neebish Island and Drummond Island all contribute to the character of the River. Fort St. Joseph was built on St Joseph Island in 1796 to protect a trading post, and ensure continued British control of the area. The fort fulfilled its role in the War of 1812.
It is of particular interest to note that the cargo carriers that travel the St. Mary’s River into and out of Lake Superior must pass by Drummond Island and cross the Drummond Island Ferry’s daily route.
Ferry passengers can watch the “Lakers” (fresh water vessels) and the “Salties’ (ocean going vessels) as they travel this local seaway between the Great Lakes.
Some of the cargo being transported on the St. Mary's River included iron ore (usually taconite pellets), coal, grain, cement, salt, sand or even dolomite from Drummond Island’s own dolomite quarry. It’s an easy day-trip from Drummond to visit the Soo Locks and see these large ships make the lift up to Lake Superior.