Lake Algonquin was a prehistoric proglacial lake that existed in east-central North America at the time of the last ice age. Parts of the former lake are now Lake Huron, Georgian Bay, Lake Superior, Lake Michigan, Lake Nipigon, and Lake Nipissing. The lake varied in size, but it was at its biggest during the post-glacial period and gradually shrunk to the current Lake Huron and Georgian Bay. About 7,000 years ago, the lake was replaced by Lake Chippewa and Lake Stanley as the glaciers retreated and 3,000 years later by the current Lakes Michigan, Huron, and Superior.