It is generally considered distinct from Northern Ontario, as it is far more densely populated and contains the majority of the province's cities, major roads, and institutions (Southern Ontario contains 94% or 11.75 million of Ontario's total population of 12.5 million people); the north, in contrast, contains more natural resources and remote wilderness. The south makes up approximately 15% of the entire land area of the province as a whole. For an inland location, it has an abundance of fresh water coastline on three of the Great Lakes (Huron, Erie and Ontario) and smaller inland lakes, notably Lake Simcoe and Lake St. Clair (part of the Great Lakes system). It is a major vineyard region and producer of Canadian wines.
Some analyses can go as far as to consider the two regions as, essentially, separate provinces, due to the level of contrast. In fact, a large portion of the north did not become part of Ontario until 1912, 45 years after Ontario entered the Confederation.
Demographics
Southern Ontario is home to almost 12 million people, compared to fewer than 800,000 in the North. This is due to many factors including the more arable land in the south, its more moderate climate, well-used transportation (water and land) routes and proximity to populated areas of the Northeastern (New York and Pennsylvania) and Midwestern United States (Michigan and Ohio).
Chapman, L.J. and Putnam, D.F. The Physiography of Southern Ontario. 3rd ed. Toronto: Ontario Ministry of Natural Resources, 1984. (Ontario Geological Survey. Special volume 2) ISBN 0-7743-9422-6.