Lake Ontario is the smallest and easternmost of North America’s five Great Lakes. It sits between the Canadian province of Ontario and New York State, with the international border running through its waters. Though smaller in surface area than the other Great Lakes, it is surprisingly deep—averaging about 283 feet—and receives water from Lake Erie through the Niagara River after it passes over Niagara Falls.glc+1

Lake Ontario is the final lake in the Great Lakes chain, draining east through the St. Lawrence River toward the Atlantic Ocean. Its shores include major cities such as Toronto, Hamilton, Rochester, and Kingston, alongside beaches, parks, farms, and the Thousand Islands near its eastern outlet. The lake supports drinking-water supplies, shipping, fishing, recreation, and a rich shoreline ecosystem for millions of people in both Canada and the United States.