What are the St. Lawrence Lowlands?

The St. Lawrence Lowlands are the flat fertile region surrounding the St. Lawrence River and the lower Great Lakes (Lake Ontario, Lake Erie, and the western shore of Lake Huron). The Lowlands extend from the Quebec City to Windsor Corridor in the south to the Canadian Shield to the north and east. Although the region covers only about 5 per cent of Canada's land area (about 180,000 square kilometres), it is home to more than half of Canada's population and the country's largest concentration of agricultural, manufacturing, and service activity.

The Lowlands have three sub-regions: the Great Lakes Lowlands of southern Ontario (Toronto, Hamilton, the Niagara Peninsula, Kitchener-Waterloo, London, Windsor); the St. Lawrence Lowlands of Quebec along the river from the Ontario border to Quebec City (Montreal, Trois-Rivieres, Quebec City, Sherbrooke); and the smaller Anticosti-Mingan-Honguedo Lowlands of the Gulf of St. Lawrence and the smaller fragment around Lake St. John (Saguenay, Lac-Saint-Jean) which is technically a separate basin within the Canadian Shield.

The geological foundation of the Lowlands is sedimentary rock laid down between 540 and 250 million years ago, when most of the region was a shallow tropical sea. Limestone, dolomite, shale, sandstone, and gypsum support the agricultural soils. Glacial deposition during the Pleistocene laid down clay, silt, gravel, and sand, including the Champlain Sea sediments deposited when the St. Lawrence Lowlands were covered by a saltwater inland sea about 13,000 to 10,000 years ago. The Champlain Sea retreat left behind some of the most fertile farmland in Canada.

Agriculture in the Lowlands includes corn and soybeans (mostly Ontario), dairy (mostly Quebec, where supply management protects 9,400 dairy farms), maple syrup (Quebec produces about 72 per cent of world supply), tobacco (mostly southwestern Ontario, in decline), fruit orchards (Niagara Peninsula, Annapolis Valley analogue, and Quebec apple country), and the Niagara Peninsula wine region. Manufacturing concentrates in southern Ontario's automotive corridor (Windsor to Oshawa), Hamilton's steel industry, and Quebec's aerospace sector around Montreal. The Quebec City to Windsor Corridor contains all five Canadian cities of more than 1 million population (Toronto, Montreal, Ottawa-Gatineau, Hamilton, and Quebec City) and is among the most densely populated regions in North America.