Lake Erie Is a Natural Great Lake

Lake Erie is entirely natural. It is the fourth-largest by surface area (25,700 km² / 9,910 sq mi) and shallowest (avg. 19 m / 62 ft) of the five Laurentian Great Lakes of North America.

Formed by glacial erosion and deposition during the last Ice Age (~10,000–14,000 years ago), it sits on the border between the United States (Michigan, Ohio, Pennsylvania, New York) and Canada (Ontario). Its outlet is the Niagara River (flowing to Lake Ontario), famously including Niagara Falls.

Human modifications (dredged channels, water-level regulation via Niagara hydropower, shoreline armor) exist, but the lake basin itself is glacial, not man-made.