Great Lakes Basin

The Great Lakes Basin consists of the Great Lakes and the surrounding lands of the states of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin in the United States, and the province of Ontario in Canada, whose direct surface runoff and watersheds form a large drainage basin that feeds into the lakes. It is generally considered to also include a small area around and beyond Wolfe Island, Ontario, at the east end of Lake Ontario, which does not drain into the Great lakes, but into the Saint Lawrence River.

The basin is home to 33 million people. The basin hosts eight of Canada's 20 largest cities, including Toronto, Hamilton, London, St. Catharines, Niagara, Oshawa, Windsor, and Barrie. The United States cities of Duluth, Milwaukee, Chicago, Gary, Detroit, Toledo, Cleveland, Erie, Buffalo, and Rochester, are located on shores of the Great Lakes.