The river's DRAINAGE BASIN covers some 1 million km2, of which 505 000 km2 is in the US, and its mean discharge of almost 10 100 m3/s is the largest in Canada. Its greatest tributary, the OTTAWA R, drains some 140 000 km2, the SAGUENAY R about 88 000 km2, the MANICOUAGAN R about 45 000 km2, the ST-MAURICE R some 43 300 km2 and the RICHELIEU R about 22 000 km2. In geological terms, the St Lawrence is a young river, whose bed is a deep gash in the Earth's crust exposed some 10 000 years ago as the glaciers receded.
The route of the explorers and main axis of NEW FRANCE, the river figured prominently in Canada's early history, and it remains the focus of settlement for much of the province of Québec. It is still the most important commercial waterway in Canada, as well as a source of electric power and natural beauty.
The St Lawrence forms much of the southwestern outline of the Canadian SHIELD, which encroaches the river at QUÉBEC CITY. At Cap-Tourmente, 40 km below Québec, the LAURENTIANS rise 579 m above the river and follow its course past Les Eboulements (770 m), where they begin to retreat inland, to the Saguenay. The S bank is generally lower, although the Appalachians approach the river at Matane and, continuing eastward, form the tableland of GASPÉ.
The westerly limit of the river itself has been set at Everett Point, Lake Ontario. The section from KINGSTON to MONTRÉAL is called the International Rapids, as sudden drops in the riverbed create a series of rapids (this portion was flooded in the 1960s, forming Lake St Lawrence). The river begins as an extended arm of Lake Ontario, choked with numerous islands, beginning with Wolfe Island and including the THOUSAND ISLANDS near Gananoque, Ont. It trends NE past Brockville, Prescott and Morrisburg to Cornwall, where it broadens to form Lake St Francis.
The Beauharnois Canal now carries shipping safely past the former rapids of Lachine and Les Cèdres to another widening of the river, Lac St-Louis, SW of Montréal. The Ottawa joins the mainstream through channels to Lac St-Louis and over a NE route via Lac des Deux Montagnes, Rivière des Mille-Iles and Rivière des Prairies.
The land between the various channels at the confluence forms the archipelago on which the city of Montréal is built. The port of Montréal has been developed since the 19th century by dredging and canals.
From Montréal to TROIS-RIVIERES, the river is generally calm and unaffected by tides. A number of long, narrow islands continue to divide the mainstream and a large cluster, similar to the group at Lake Ontario, lies at the mouth of the Richelieu River at Sorel. The river broadens into Lac St-Pierre, some 15 km wide, and narrows again at Trois-Rivières, at the mouth of the St-Maurice River. From here to Québec, the freshwater flow becomes reversible with the tides.
The river constricts at Québec where a promontory commands the entire upper course. The military value of the site was appreciated long before European settlement began.
Past Québec the river divides to encircle Ile d' ORLÉANS and steadily widens to 15 km at Cap-Tourmente, almost 25 km at Ile-aux- COUDRES. The water becomes brackish and tides are high. Near the mouth of the Saguenay River, the riverbed drops dramatically from 25 m to 350 m, forming a drowned valley in the lower estuary. The freshwater flow mingles with cold arctic saltwater. The town of TADOUSSAC sits on a terrace of sand and clay at the confluence, but the rugged Precambrian N shore is sparsely settled.
The S shore of the estuary, which forms a great curve towards Gaspé, is more open towards its hinterland, and major roads, including the TRANS-CANADA HIGHWAY, head inland from Rivière-du-Loup, Trois-Pistoles, Rimouski and Matane.
At Pointe-des-Monts, about 70 km E of Baie-Comeau and the mouth of the Manicouagan River, the N shore turns dramatically NNE for about 100 km to SEPT-ILES, near the mouth of the MOISIE R. The river doubles in width to over 100 km, forming a deep, broad submarine valley, in which strong currents pour in from the gulf along the N shore and sweep counterclockwise back to the E. The saline water of the estuary discourages ice, and the port of Sept-Iles is open year-round, despite its northerly location.
According to the ROYAL PROCLAMATION OF 1763, a line from the mouth of Rivière St-Jean on the N shore past the W tip of Ile d' ANTICOSTI to Cap des Rosiers on Gaspé marks the end of the river and the beginning of the gulf.
Over the course of the river, the vegetation varies from deciduous, mixed and coniferous forest to taiga. There are sandbank grasses in the freshwater course, and seaweed and other saltwater plants in the middle and maritime estuary. Fish include smelt, sturgeon and herring. Beluga whales inhabit the lower course, on which walrus was once also abundant. Massive flocks of migratory birds use the sandbanks or river reefs as seasonal stops, including most of the world's greater snow geese, which nest on the tidal marshes at Cap-Tourmente.
Sedentary Indian groups - likely Iroquoian - were settled at the present sites of Québec [ STADACONA ] and Montréal [ HOCHELAGA ] at the time of Jacques CARTIER's first explorations in the area in 1535. They had inexplicably disappeared by the time CHAMPLAIN founded Québec in 1608, possibly dispersed by the nomadic Montagnais, Etchemin and Algonquin, with whom the French established a lucrative trading alliance.
Jacques Cartier had discovered the river in 1535, with the help of Indian guides who took him past Anticosti, which he had believed was a peninsula. He built 2 transient camps near Stadacona in 1535 and 1541, but it was not until 1608 that the French foothold was secure.
The St Lawrence River provides almost the only riverine entrance to the heart of the continent, and French explorers and traders used it to establish a colonial empire that stretched beyond Lake Superior. By 1760 most of the riverbank from Québec to Montréal was patterned with the long, narrow strips of the SEIGNEURIAL SYSTEM, with the seigneury of Beaupré marking the eastern limit of settlement.
The river system was suited to the carriage of buoyant softwood logs, and in the 19th century the river became the main artery of the TIMBER TRADE. Montréal and Québec City grew into major commercial centres, as wheat and flour from UPPER CANADA were carried down the river. Under the leadership of the NORTH WEST CO, the fur traders pushed the "Empire of the St Lawrence" all the way to the basin of the Mackenzie River.
Donald CREIGHTON and others have argued that the E-W axis of the St Lawrence, which provided a counterpoise to the N-S affinity offered by much of the continent's geography, helped make possible the future nation of Canada. Today, with the development of the ST LAWRENCE SEAWAY, the river links a vast area of Canada and the US with the rest of the world. It is still, as Cartier called it, "the great river of Canada."
See also ST LAWRENCE LOWLAND.
Author JAMES MARSH
Links to Other Sites
The website for the Historica-Dominion Institute, parent organization of The Canadian Encyclopedia and the Encyclopedia of Music in Canada. Check out their extensive online feature about the War of 1812, the "Heritage Minutes" video collection, and many other interactive resources concerning Canadian history, culture, and heritage.
Library and Archives Canada
The website for Library and Archives Canada. Offers searchable online collections of textual documents, photographs, audio recordings, and other digitized resources. Also includes virtual exhibits about Canadian history and culture, and research aids that assist in locating material in the physical collections.
The St. Lawrence River and Climate Warming
An online feature about the impact of climate change on St Lawrence River region. From Environment Canada.
Watch the Heritage Minute about French explorer Jacques Cartier from the Historica-Dominion Institute. See also related online learning resources.
This nicely illustrated website is dedicated to the history of Fort Frontenac. From the Cataraqui Archaeological Research Foundation.
Grosse Île and the Irish Memorial National Historic Site of Canada
This Parks Canada site commemorates the Port of Québec’s role as an immigration and quarantine centre from the early 19th century to the First World War. Nicely illustrated and detailed notes about Irish immigration, the typhoid epidemic of 1847 and the achievements of public health official Dr. Frederick Montizambert. Includes a virtual tour of Grosse Île facilities.
Take a virtual tour of historic Soulanges Canal in Québec.
Raid on Deerfield
A narrated history of the 1704 Raid on Deerfield and its aftermath from Native and European perspectives. Also features fascinating stories about Native societies, cultures, trade practices, and traditions. This multimedia website is from the Memorial Hall Museum in Deerfield, Massachusetts.
An extensive information source about the geological history, human settlement patterns, earth and water resources, and natural hazards found in locations across the country. Click on the red symbols on the interactive map of Canada to explore aerial landscapes, maps, photos, colourful online posters, and more. A Geoscape Canada website from Natural Resources Canada.
Maurice Lamontagne Institute
Learn about oceanographic research and management programs in the Gulf of St. Lawrence and northern Québec. A Fisheries and Oceans Canada website.
The Montréal Biodôme invites you to take a virtual tour of its ecosystems.
Lost Villages Historical Society
The website for the Lost Villages Historical Society, an organization dedicated to preserving the history of the St. Lawrence River communities that existed prior to the building of the St. Lawrence Seaway and Power Project in the late 1950s.
Glossary: Lake Ontario-St Lawrence River system
A glossary of key terms related to environmental issues in the Lake Ontario-St Lawrence River system.
Québec Fortified City: Geological and Historical Heritage
A well-illustrated Geological and Historical Heritage Fieldtrip Guidebook for the fortified City of Québec. See the glossary at the end of this document for a definition of key geological terms. From Natural Resources Canada.
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