About 13,000 years ago the melting glaciers that covered Minnesota and Canada created a vast lake, bigger than all the Great Lakes of today combined. Geologists later named this Lake Agassiz (AH-ga-see), for the Swiss geologist Louis Agassiz. The lake drained twice: first to the south, to form the channel of the Minnesota River and the Upper Mississippi in the Twin Cities, and then, 1,600 years later, to form the course of the Red River of the North.