Which Great Lake lies at the lowest elevation?

Lake Ontario lies at the lowest elevation of the Great Lakes.

Its average surface elevation is about 74 metres above sea level, lower than that of the other four lakes. Lake Ontario receives water from Lake Erie through the Niagara River and releases it through the St. Lawrence River, which carries the Great Lakes system toward the Atlantic Ocean.

Despite being the smallest Great Lake by surface area, Ontario is comparatively deep. Its deepest point is about 244 metres, and its elongated basin lies between southern Ontario and northern New York. Toronto, Canada’s largest city, is situated on its northwestern shore.

The lake’s low elevation is part of the natural staircase formed by the Great Lakes. Water descends from Superior through the connected lakes and rivers before entering the St. Lawrence. A common mistake is to equate smallest surface area with shallowest depth: Lake Ontario is smallest by area but much deeper than Lake Erie.