Lake Nipissing
About 9000 B.C., when the glacial ice began to retreat from this area for the last time, the Nipissing basin formed an easterly extension of an ancestral Georgian Bay. The weight of ice had depressed the land, thus providing an outlet to the Ottawa Valley for the waters of the prehistoric Upper Great Lakes basin. Owing to the gradual uplift of the land following the retreat of the ice, the eastward flow ceased about 2000 B.C. Thereafter Lake Nipissing drained westward, forming the French River which later became a link in the historic canoe route to the West.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.