What is the significance of the St. Lawrence River?

The St. Lawrence River is one of Canada's most important waterways, flowing about 1,200 kilometres from the eastern outflow of Lake Ontario to the Gulf of St. Lawrence and the Atlantic Ocean. It drains the Great Lakes basin, the largest freshwater system in the world by surface area, and forms the natural border between Ontario and New York for part of its course before entering Quebec. Major Canadian cities along the river include Kingston, Cornwall, Montreal, Trois-Rivieres, and Quebec City.

The St. Lawrence is the historic gateway to Canada. Jacques Cartier sailed up the river in 1535 to the village of Stadacona, the future site of Quebec City, and to Hochelaga, the future site of Montreal. Samuel de Champlain founded Quebec City on the river's north bank in 1608. Through the seventeenth, eighteenth, and nineteenth centuries the river was the principal route for the fur trade, the Loyalist migration, the timber trade, and waves of European immigration that shaped the Canadian population. Pier 21 in Halifax became the eastern arrival point in the twentieth century, but the St. Lawrence ports remained essential.

The St. Lawrence Seaway, opened jointly by Queen Elizabeth II and U.S. President Dwight D. Eisenhower on June 26, 1959, allows ocean-going vessels to travel from the Atlantic to Lake Superior, a distance of 3,700 kilometres. The Seaway comprises 15 locks (13 Canadian and 2 American), bypassing rapids and the Niagara escarpment. The St. Lawrence Seaway Management Corporation operates the Canadian section, while the Saint Lawrence Seaway Development Corporation runs the U.S. section. About 200 million tonnes of cargo move through the Seaway annually, primarily grain, iron ore, steel, and coal.

The river is also a cultural and constitutional touchstone. Section 35 of the Constitution Act, 1982 protects Indigenous rights of the Mohawk, Algonquin, Innu, and other nations along the river. The 1990 Mohawk crisis at Kanesatake and Kahnawake centred on disputed land and treaty rights along the St. Lawrence. Modern environmental management of the river is shared by the federal government (Fisheries and Oceans Canada, Transport Canada), Quebec, Ontario, and Indigenous co-management arrangements.