The St. Lawrence River (, ) is a large international river in the middle latitudes of North America connecting the Great Lakes with the North Atlantic Ocean. Its waters flow in a northeasterly direction from Lake Ontario to the Gulf of St. Lawrence, traversing Ontario and Quebec in Canada and New York in the United States. A portion of the river demarcates the Canada–United States border.

As the primary drainage outflow of the Great Lakes Basin, the St. Lawrence has the second-highest discharge of any river in North America (after the Mississippi River) and the 16th-highest in the world. The estuary of the St. Lawrence is often cited by scientists as the largest in the world. Significant natural landmarks of the river and estuary include the 1,864 river islands of the Thousand Islands, the endangered whales of Saguenay–St. Lawrence Marine Park, and the limestone monoliths of the Mingan Archipelago.

Long a transportation route to Indigenous peoples, the St. Lawrence River has played a key role in the history of Canada and in the development of cities such as Montreal and Quebec City. The river remains an important shipping route as the backbone of the St. Lawrence Seaway, a lock-and-canal system that enables world marine traffic to access the inland ports of the Great Lakes Waterway.

Etymology The river has historically been given a variety of different names by local First Nations. Beginning in the 16th century, French explorers visited what is now Canada and gave the river names such as the Grand fleuve de Hochelaga and the Grande rivière du Canada, where fleuve and rivière are two French words (fleuve being a river that flows into the sea).

The river's present name has been used since 1604, when it was recorded on a map by Samuel de Champlain. Champlain opted for the names Grande riviere de sainct Laurens and Fleuve sainct Laurens in his writings, supplanting the earlier names. In contemporary French, the name is rendered as the fleuve Saint-Laurent. The name Saint-Laurent (Saint Lawrence) was originally applied to the eponymous bay by Jacques Cartier upon his arrival into the region on the 10th of August feast day for Saint Lawrence in 1535.

Indigenous people use the following names: Innu-aimun, the language of Nitassinan, refer to it as Wepistukujaw Sipo/Wepìstùkwiyaht sīpu. The Abenaki call it Moliantegok/Moliantekw ("Montréal River"), Kchitegw/Ktsitekw/Gicitegw ("Great River"), or Oss8genaizibo/Ws8genaisibo/Wsogenaisibo ("River of the Algonquins"). In the Mohawk language, it is Roiatatokenti, Raoteniateara, Ken'tarókwen, or Kaniatarowanénhne. Tuscarora people call it Kahnawáˀkye or Kaniatarowanenneh ("Big Water Current").Rudes, B. Tuscarora English Dictionary Toronto: University of Toronto Press, 1999 Algonquin people call it "the Walking Path" or Magtogoek, or Kitcikanii sipi, the "Large Water River". The Wendat Nation call it Lada8anna or Laooendaooena'''. The Atikamekw of Nitaskinan refer to it as Micta sipi ("Huge River").

Geography

Marine weather In winter, the St. Lawrence River begins producing ice in December between Montreal and Quebec City. The prevailing winds and currents push this ice towards the estuary, and it reaches the east of Les Méchins at the end of December. Ice covers the entire Gulf of St. Lawrence in January and February.

Ice helps navigation by preventing the formation of waves, and therefore spray, and prevents the icing of ships.

Watershed With the draining of the Champlain Sea, due to a rebounding continent from the Last Glacial Maximum, the St. Lawrence River was formed. The Champlain Sea lasted from about 13,000 to about 10,000 years ago and was continuously shrinking during that time, a process that continues today.Lake Champlain Basin Atlas: Geology Page The head of the St. Lawrence River, near Lake Ontario, is home to the Thousand Islands.

Today, the St. Lawrence River begins at the outflow of Lake Ontario and flows adjacent to Cape Vincent, Gananoque, Clayton, Alexandria Bay, Brockville, Morristown, Ogdensburg, Massena, Cornwall, Montreal, Trois-Rivières, and Quebec City before draining into the Gulf of St. Lawrence, often given as the largest estuary in the world. The estuary begins at the eastern tip of Île d'Orléans, just downstream from Quebec City. The river becomes tidal around Quebec City.

The St. Lawrence River runs from the farthest headwater to the mouth and from the outflow of Lake Ontario. These numbers include the estuary; without the estuary, the length from Lake Ontario is . The farthest headwater is the North River in the Mesabi Range at Hibbing, Minnesota. Its drainage area, which includes the Great Lakes, the world's largest system of freshwater lakes, is , of which are in Canada and are in the United States. The basin covers parts of Ontario and Quebec in Canada, parts of Minnesota, Wisconsin, Illinois, Indiana, Ohio, Pennsylvania, New York, Vermont, and nearly the entirety of Michigan in the United States. The average discharge below the Saguenay River is . At Quebec City, it is . The average discharge at the river's source, the outflow of Lake Ontario, is .

The St. Lawrence River includes Lake Saint Francis at Salaberry-de-Valleyfield, Lake Saint-Louis south of Montreal, and Lake Saint Pierre east of Montreal. It encompasses four archipelagoes: the Thousand Islands chain near Alexandria Bay, New York, and Kingston, Ontario; the Hochelaga Archipelago, including the Island of Montreal and Île Jésus (Laval); the Lake St. Pierre Archipelago (classified a biosphere world reserve by the UNESCO in 2000),Lac Saint-Pierre et son archipel . Pleinairalacarte.com (2008-11-07). Retrieved 2013-07-12. and the smaller Mingan Archipelago. Other islands include Île d'Orléans near Quebec City and Anticosti Island north of the Gaspé. It is the second-longest river in Canada.

Lake Champlain and the Ottawa, Richelieu, Saint-Maurice, Saint-François, Chaudière, and Saguenay Rivers drain into the St. Lawrence.

The St. Lawrence River is in a seismically active zone where fault reactivation is believed to occur along late Proterozoic to early Paleozoic normal faults related to the opening of the Iapetus Ocean. The faults in the area are rift-related and comprise the Saint Lawrence rift system.

According to the United States Geological Survey, the St. Lawrence Valley is a physiographic province of the larger Appalachian division, containing the Champlain section. However, in Canada, where most of the valley is, it is instead considered part of a distinct St. Lawrence Lowlands physiographic division and not part of the Appalachian division.

Sources

The source of the North River in the Mesabi Range in Minnesota (Seven Beaver Lake) is considered to be the source of the St. Lawrence River. Because it crosses so many lakes, the water system frequently changes its name. From source to mouth, the names are:

The St. Lawrence River also passes through Lake Saint-Louis and Lake Saint-Pierre in Quebec.

Tributaries

The St. Lawrence River is the largest tributary of the Great Lakes.

The St. Lawrence River tributaries are listed upstream from the mouth. The major tributaries of the interlake sections are also shown, as well as the major rivers that flow into the Great Lakes. Great Lakes tributaries are listed in alphabetical order.

The list includes all tributaries with a drainage area of at least 1,000 km2 and an average flow of more than 10 m3/sec. Left tributary Right tributary Length (km) Basin size (km2) Average discharge (m3/s)St. Lawrence RiverGodbout1121,930.144.4Frankquelin67.5582.912.1Manicouagan22145,9081,020Outardes49919,057400Mitis511,806.437Betsiamites44418,984.1366.7Laval42641.613Rivière du Sault aux Cochons1281,94638.7Rimouski119.21,63530.8Portneuf552,457.652.3Rivière des Escoumins84810.517.5Rivière des Trois-Pistoles4396618.4Verte507.910.2Saguenay17087,635.41,893.9Rivière du Loup101.31,05918.5Malbaie1611,861.139.1Rivière-Ouelle73.4850.616.8Rivière du Gouffre76.11,010.123.5Montmagny (Rivière du Sud)86.51,994.646.7Sainte-Anne971,07731.5Montmorency103.71,157.635.6Saint-Charles25483.413.6Etchemin1241,443.434.5Chaudière1856,682146.4Jacques-Cartier1782,51571.3Rivière du Chêne80.6855.921.1Sainte-Anne1232,753.373.4Batiscan1964,690107.1Bécancour2102,60763.2Saint-Maurice56341,994.3730Nicolet1373,38077.8Rivière du Loup1021,642.927.8Saint François21810,230237.8Yamaska1604,784110.1Maskinongé401,205.721.3Richelieu12423,717.7455.8L'Assomption2004,22078.6Ottawa1,271147,405.81,948.8Châteauguay1212,466.743.8Rivière aux Saumons70.61,065.220.2St. Regis River1382,219.644Raquette2353,25074.4Grasse1171,657.932.9Oswegatchie2204,12088.3Gananoque909.512.2NiagaraTonawanda Creek1401,70027.2DetroitRouge2041,58010.7St. Clair RiverSydenham1652,727.614.3Belle118.3556.44.4Black130.41,821.99.2Great LakesLake OntarioBlack2014,964.8159.5Credit901,0008.1Genesee2536,507.7107.5Humber1001,008.47.5Moira982,73632.6Napanee601,099.212.6Niagara58682,350.95,885Oak Orchard95.2804.313Oswego3813,266255Salmon1351,53418.2Salmon71820.521.9Sandy Creek53501.911Trent9013,014.7154.6Welland1401,136.48.7Lake ErieBlack681,2179.8Buffalo131,186.417.4Cattaraugus Creek1091,510.124Cuyahoga136.62,377.629Detroit45595,0525,300Grand2806,763.845Grand165.31,873.623.8Huron2102,145.220.4Huron241,055.68.8Maumee22016,460164.1Portage66.81,574.611.3Raisin2242,78022.8Sandusky2143,262.126.1Lake St. ClairClinton1341,970.919.8St. Clair River65.2583,508.75,200Thames2735,82552.9Lake HuronAu Gres75.21,2627.2Au Sable2225,468.536.4Ausable641,1428.1Cheboygan613,880.132.5French11019,100207Garden1,061.714.6Magnetawan1753,041.924.7Maitland1502,59221.4Mississagi2669,270118Musquash294,591.743.7Nottawasaga1203,082.418.8Saginaw–Shiawassee21615,525.6136.7St. Marys River119.9211,833.32,135Sauble1,109.77.6Saugeen1604,12081.8Seguin401,0239.7Serpent1,49510.2Severn306,039.256.9Spanish33813,368.3150Thessalon1,125.48.3Thunder Bay121.33,382.119.2Whitefish1,318.97.2Lake MichiganBurns Waterway35.61,033.28.9Calumet661,183.810Cedar1081,158.36.9Elk1211,379.512.5Escanaba842,39028.1Ford1741,414.710.7Fox32016,650143.8Grand40615,206.6143Kalamazoo2105,23052.8Manistee3104,60047.5Manistique114.63,78052.7Manitowac57.61,552.410.6Menomonee18710,56999.6Milwaukee1672,271.517.1Muskegon3487,029.860.8Oconto91.62,474.919.8Pere Marquette102.82,074.618Peshtigo2192,856.321.9Shebaygan1301,2268.8St. Joseph River34012,130142.2White381,45813Lake SuperiorAgawa1021,057.829.1Aguasabon70964.316.8Bad119.62,659.844.7Batchawana951,396.136.7Black66.1724.315.1Black Sturgeon722,815.643.1Brule65699.710Chipewa40920.922.4Dog50.91,333.528Goulais702,07142.1Gravel700.112.1Kaministiquia957,903.199.4Little Pic1,459.121Magpie–Michipicoten817,446.7145.8Montreal1303,45284Montreal76.9861.912.8Nemadji113.91,158.418.6Nipigon4825,645.4383.6Old Woman558.810.9Ontonagon403,720.275.8Pic1886,430109.9Pigeon801,610.625.1Presque Isle67.81,088.920.3Pukaskwa801,308.324.6Saint Louis3099,410146.7Sand56537.713Steel1701,298.818.3Sturgeon1711,892.243.1Tahquamenon143.42,25846.3Two Hearted3857511.7White1405,228.395.7Wolf650.210Source

Discharge

YearAverage discharge Quebec City Pointe-des-Monts20072008200920102011201220132014201520162017201820192020202120222023

Biodiversity The diversity of the St. Lawrence River includes: 19 species of marine mammals More than 230 species of birds Nearly 35 species of amphibians and reptiles 200 species of freshwater and saltwater fish (including 19 sharks and rays) 2200 invertebrates in the estuary and its gulf (sponges, jellyfish, corals, crustaceans, etc.) Nearly 2000 vascular plants

Marine mammals

Large marine mammals travel in all the seas of the earth. The observation of these animals concern fishermen and shipping industry, exercise a fascination for laymen, and are subjects for study by scientists.

Thirteen species of cetaceans frequent the waters of the estuary and the Gulf of St. Lawrence: Northern bottlenose whale Delphinapterus leucas (Beluga Whale) Sperm whale Atlantic white-sided dolphin White-beaked dolphin