The St. Lawrence Seaway is a system of locks, canals, and channels in Canada and the United States that permits oceangoing vessels to travel from the Atlantic Ocean to the Great Lakes of North America, as far inland as Duluth, Minnesota, at the western end of Lake Superior. The seaway is named for the St. Lawrence River, which flows from Lake Ontario to the Atlantic Ocean. Legally, the seaway extends from Montreal, Quebec, to Lake Erie, and includes the Welland Canal. Ships from the Atlantic Ocean are able to reach ports in all five of the Great Lakes, via the Great Lakes Waterway.

The Welland Canal is a ship canal in Ontario, Canada, and part of the St. Lawrence Seaway and Great Lakes Waterway. The canal traverses the Niagara Peninsula between Port Weller on Lake Ontario, and Port Colborne on Lake Erie, and was erected because the Niagara River—the only natural waterway connecting the lakes—was unnavigable due to Niagara Falls. The Welland Canal enables ships to ascend and descend the Niagara Escarpment, and has followed four different routes since it opened.