St. Marys River (Michigan-Ontario) in the context of "Sault Ste. Marie, Michigan"

The Great Lakes Waterway (GLW) is a system of natural channels and artificial locks and canals that enable navigation between the North American Great Lakes. Although all of the lakes are naturally connected as a chain, water travel between the lakes was impeded for centuries by obstacles such as Niagara Falls and the rapids of the St. Marys River.

Its principal civil engineering works are the Welland Canal between Lakes Ontario and Erie, and the Soo Locks between Huron and Superior. Dredged channels were constructed in the St. Marys River, the Detroit River, Lake St. Clair and the St. Clair River between Huron and Erie. Usually, one or more U.S. Coast Guard icebreakers help keep the water passage open for part of the fall and early winter, although shipping usually ceases for two to three months thereafter. The St. Lawrence Seaway allows navigable shipping from the GLW to the Atlantic Ocean, while the Illinois Waterway extends commercial shipping to the Mississippi River and the Gulf of Mexico. The Great Lakes Waterway is co-administered by the governments of Canada and the United States.

The North Channel is the body of water along the north shore of Lake Huron, in the Canadian province of Ontario and the state of Michigan in the United States of America. It stretches approximately 160 nautical miles (300 km) and is bordered on the east by Georgian Bay, on the west by the St. Marys River, to the north by the eastern Algoma District and part of the Sudbury District, and to the south by the islands of Manitoulin, Cockburn, Drummond and St. Joseph. At its widest point it is over 30 km (20 miles) wide.

In addition to Georgian Bay, the North Channel is connected to the main body of Lake Huron by the False Detour Channel and the Mississagi Strait, which separate the above-noted islands.

The Sault Ste. Marie Canal is a National Historic Site in Sault Ste. Marie, Ontario, and is part of the national park system, managed by Parks Canada. It includes a lock to bypass the rapids on the St. Marys River.

The first canal near the site was built in 1798, but was destroyed in 1814 during the War of 1812. The present canal dates to 1895, and formed part of the shipping route from the Atlantic Ocean to Lake Superior, along with the two locks on the US side of the river. One of the walls of the lock collapsed in 1987 and the canal was closed to traffic.