The Saint Lawrence Valley was once home to the Iroquois,
Algonquin, Huron, Mohawk, Abnake, and Montagnais peoples. The first European to visit the Saint Lawrence River was the French explorer Jacques Cartier, in 1535. The first permanent European settlement on the Saint Lawrence was established at the site of present-day Québec City by French explorer Samuel de Champlain in 1608.
The river remained in French hands during the 17th and
18th centuries, when it served as the main route of the fur trade, transporting pelts from the Great Lakes and the Saint Lawrence Valley for shipment to Europe. The British gained control of the region at the end of the French and Indian War in 1763. In 1867 Britain's Parliament passed the British North America Act, which formed the Dominion of Canada and included
the Saint Lawrence Valley. Today most of the valley lies within the province of Québec.
The Saint Lawrence (river) (French Saint-Laurent), river in eastern North America. The chief outlet of the Great Lakes, the Saint Lawrence flows northeast from Lake Ontario to the Gulf of Saint Lawrence on the North Atlantic Ocean, a distance of about 1300 km (about 800 mi).
As part of the Saint Lawrence Seaway, a system of canals, locks, and dredged channels built to allow the passage of oceangoing vessels, the Saint Lawrence River serves
as a major water route to the interior of the United States and Canada, linking the Great Lakes with the Atlantic Ocean.
The total drainage area of the Saint Lawrence River is about 1,030,000 sq km (about 398,000 sq mi). Of this, approximately 750,000 sq km (approximately 290,000 sq mi) flows into the river through the Great Lakes, and about 250,000 sq km (about 97,000 sq mi) drains directly to the Saint Lawrence.
The average flow of the Saint Lawrence is 14,165 cu m per second (500,200 cu ft per second).
The Saint Lawrence River begins at the outlet of Lake Ontario and flows to the northeast. In its upper course, which includes the scenic Thousand Islands, the river forms the boundary between the province of Ontario and the state of New York. The river then widens into Lake Saint Francis, which serves for a short distance as the border between the provinces of Ontario and Québec, before flowing wholly in Québec for the remainder of its course. At Montréal the river expands to create Lake
St.-Louis, and below Sorel it forms the much larger Lac Saint-Pierre. Below Québec the Saint Lawrence broadens from a width of about 3 km (about 2 mi) to about 145 km (about 90 mi) at its mouth.
Ocean tides extend up the river for about 800 km (about 500 mi) to the city of Trois-Rivières. The main tributaries of the Saint Lawrence are the Ottawa, Saint-Maurice, and Saguenay rivers from the north, and the Richelieu, Saint-François, and Chaudière rivers from the south. The river is home to a great variety of fish, including sturgeon, smelt, and herring. Belugas (white whales) live near the Gulf of Saint Lawrence.
The Saint Lawrence Valley is one of the most densely
populated parts of Canada, containing about 25 percent of the nation's population. The two largest cities in Québec province, Montréal and Québec City, lie on the north bank of the river. Montréal lies just below the Lachine Rapids, which were the upstream limit of navigation by oceangoing vessels before the completion, in 1959, of the Saint Lawrence Seaway.
Montréal rose to prominence as Canada's principal eastern seaport. Today large vessels must still stop at Montréal, while medium-sized oceangoing ships may continue to the Great Lakes. Icebreakers keep the ports of Montréal and Québec open year-round, but ice prevents navigation on the upper river from December to April.
Industry, especially aluminum smelting, paper milling, and general manufacturing, is the most important economic activity in the Saint Lawrence Valley. The valley lowlands contain some fertile farmland, producing dairy goods, fruit, potatoes, and grain. Tourism is also important, especially in
Montréal, the Thousand Islands, and Québec City.
Hydroelectric power is generated in the area between Kingston, Ontario, and Montréal. Industrial and municipal discharges in and around Trois-Rivières, Montréal, and Québec, as well as contamination on the Ottawa River, contribute some pollution to the Saint Lawrence. However, because of the river's large
volume of flow, the pollution concentrations are not as severe as those in many other rivers.