St. Lawrence River Facts - Rivers of North America

The St. Lawrence River as seen in Quebec, Canada.

The Saint Lawrence River is one of the largest rivers in North America which, together with the Great Lakes, form a hydrographic system that penetrates over 3,050 kilometers into North America. It flows in a north east direction and connects the Great Lakes and the Atlantic Ocean to form a main drainage outflow of the Great Lakes Drainage Basin which covers about 1 million square kilometers. Saint Lawrence River flows through Quebec and Ontario in Canada and also forms part of the border line between Ontario and New York. The river is also an important commercial seaway with several economic benefits.

4. Physical Description

The St. Lawrence River starts at the outflow of Lake Ontario and passes through several towns and cities in Quebec and Ontario before emptying into Gulf of Saint Lawrence. The river runs for about 1,900 miles from the furthest headwaters to the mouth and 744 miles from Lake Ontario’s outflow. St. Lawrence River drains an area, including the Great Lakes, of 519,998 square miles of which over 324,000 square miles is in Canada and the rest is in the US. The river includes several lakes such as Saint-Louis, Saint Francis, and Saint Pierre Lakes. It also encompasses four archipelagoes including the Thousand Islands, Hochelaga, and Mingan Archipelago.

3. Historical Significance

St. Lawrence River was an important source of whales for the Bosques who settled at the St. Lawrence Gulf in the late 16th century. The Bosque whalers traded with the indigenous Americans and built settlements along the Canadian coast and into the river valley. In the 17th century, the river was the main waterway for European exploration of the interior of North America which was first pioneered by Samuel de Champlain, a French explorer. The control of Saint Lawrence River was significant for the British strategy to take control of New France during the Seven Years’ War. The lower St. Lawrence River was a battlefield in the Battle of Saint Lawrence involving the submarine and anti-submarine.

2. Major Settlements

The shore of St. Lawrence River is home to over 80% of Quebec population. About 50% of the Quebec population depends on the water from the watercourses for their domestic use. The first permanent settlement on the St. Lawrence was established in the early 17th century by the French explorer Samuel de Champlain. The river was a French territory in the 17th and 18th century serving as the main transportation route. Today, St. Lawrence River valley is one of the most populated areas of Canada accounting for over 20% of the Canadian population. Montreal and Quebec City lie north of the river bank. Several industries including aluminum smelting and general manufacturing are also located along the river valley and are important economic activities in the area.

1. Water Quality

About 40% of St. Lawrence River has been assessed for water quality. The water quality of St. Lawrence Watershed is characterized by the atmospheric deposition of pollutants that originate mainly outside the St. Lawrence River Basin. Acid rain and mercury deposition are major issues in the watershed. The intensive agricultural activities have had a direct impact on the river with large quantities of chemicals used in the farms finding their way to the river. Hazardous waste and other industrial chemicals are also a concern to the river basin. However, the water of St. Lawrence River is still considered fit for domestic use and supports hundreds of households in the areas.


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