The Great Lakes Waterway is a system of channels and canals that makes all of the Great Lakes accessible to oceangoing vessels. Its principal civil engineering components are the Welland Canal, bypassing Niagara Falls between Lake Ontario and Lake Erie, and the Soo Locks, bypassing the rapids of the St. Marys River between Lake Superior and Lake Huron, at Sault Sainte Marie. Maintained channels serve the St. Clair River and Detroit River between Lake Huron and Lake Erie. A United States Coast Guard icebreaker helps keep the passage open for much of the winter, although shipping usually ceases for 2 or 3 months each year.
The Great Lakes Waterway is supplemented by the Saint Lawrence Seaway, which makes the Saint Lawrence River navigable from Montreal to Kingston, Ontario. The two waterways are often jointly referred to as the St. Lawrence Seaway. The Great Lakes Waterway has larger locks and deeper drafts than the St. Lawrence Seaway with the result that a number of lake freighters are confined to the lakes, being small enough to operate on the Waterway but too large to pass down the Seaway.
The Great Lakes Waterway is co-administered by Canada and the United States.