Early Lake Erie was a prehistoric proglacial lake

Proglacial lake

In geology, a proglacial lake is a lake formed either by the damming action of a moraine or ice dam during the retreat of a melting glacier, or by meltwater trapped against an ice sheet due to isostatic depression of the crust around the ice...

 that existed at the end of the last ice age

Ice age

An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

 approximately 13,000 years ago. The early Erie fed waters to Glacial Lake Iroquois

Glacial Lake Iroquois

Glacial Lake Iroquois was a prehistoric proglacial lake that existed at the end of the last ice age approximately 13,000 years ago.The lake was essentially an enlargement of the present Lake Ontario that formed because the St. Lawrence River downstream from the lake was blocked by the ice sheet...

.

Then ancient lake was similar in size to the current lake during glacial retreat, but some period the western half of the lake was covered with ice.

Early-period Lake Erie was made up of smaller lakes (Lakes Warren, Wayne, Maumee and Lundy) with lower depths. Much of the ancient lake bed is now northern Ohio

Ohio

Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...

.