Saint Lawrence River  The Saint Lawrence River (; ; , meaning "big waterway") is a large river in the middle latitudes of North America. The Saint Lawrence River flows in a roughly north-easterly direction, connecting the Great Lakes with the Atlantic Ocean and forming the primary drainage outflow of the Great Lakes Basin. It traverses the Canadian provinces of Quebec and Ontario, and is part of the international boundary between Ontario, Canada, and the U.S. state of New York. This river provides the basis for the commercial Saint Lawrence Seaway. With the draining of the Champlain Sea, due to a rebounding continent from the Last Glacial Maximum, the Saint Lawrence River was formed. The Champlain Sea lasted from about 13,000 years ago to about 10,000 years ago and was continuously shrinking during that time, a process that continues today. Today, the Saint Lawrence River begins at the outflow of Lake Ontario and flows adjacent to Gananoque, Brockville, Morristown, Ogdensburg, Massena, Cornwall, Montreal, Trois-Rivières, and Quebec City before draining into the Gulf of Saint Lawrence, 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 Saint 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 ca. 500 km (ca. 300 mi). 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 is in Canada and is in the United States. The basin covers parts of Ontario and Quebec in Canada, parts of Illinois, Indiana, Minnesota, New York, Ohio, Pennsylvania, Vermont, and Wisconsin, and nearly the entirety of the state 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 Saint Lawrence River includes Lake Saint-Louis south of Montreal, Lake Saint Francis at Salaberry-de-Valleyfield and Lac 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 biosphere world reserve by the UNESCO in 2000) and the smaller Mingan Archipelago.