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Geography

The thinly populated Canadian Shield, which dominates the northwestern and central portions of the province, comprises over half the land area of Ontario. Although this area mostly does not support agriculture, it is rich in minerals, partly covered by the Central and Midwestern Canadian Shield forests, and studded with lakes and rivers. Northern Ontario is subdivided into two sub-regions: Northwestern Ontario and Northeastern Ontario.

The virtually unpopulated Hudson Bay Lowlands in the extreme north and northeast are mainly swampy and sparsely forested.

Southern Ontario, which is further sub-divided into four sub-regions: Central Ontario (although not actually the province's geographic centre), Eastern Ontario, Golden Horseshoe and Southwestern Ontario (parts of which were formerly referred to as Western Ontario).

Despite the rarity of mountainous terrain in the province, there are large areas of uplands, particularly within the Canadian Shield which traverses the province from northwest to southeast and also above the Niagara Escarpment which crosses the south. The highest point is Ishpatina Ridge at 693 metres (2,274 ft) above sea level in Temagami, Northeastern Ontario. In the south, elevations of over 500 m (1,640 ft) are surpassed near Collingwood, above the Blue Mountains in the Dundalk Highlands and in hilltops near the Madawaska River in Renfrew County.

The Carolinian forest zone covers most of the southwestern region of the province. The temperate and fertile Great Lakes-Saint Lawrence Valley in the south is part of the Eastern Great Lakes lowland forests ecoregion where the forest has now been largely replaced by agriculture, industrial and urban development. A well-known geographic feature is Niagara Falls, part of the Niagara Escarpment. The Saint Lawrence Seaway allows navigation to and from the Atlantic Ocean as far inland as Thunder Bay in Northwestern Ontario. Northern Ontario covers approximately 87% of the province's surface area; conversely, Southern Ontario contains 94% of the population.

Point Pelee is a peninsula of Lake Erie in southwestern Ontario (near Windsor and Detroit, Michigan) that is the southernmost extent of Canada's mainland. Pelee Island and Middle Island in Lake Erie extend slightly farther. All are south of 42°N – slightly farther south than the northern border of California.