A map of the Laurentide era glacial Lake Agassiz in the present day region of the northern United States and southern Saskatchewan, Manitoba, and Ontario. The lake was present during the last glacial period, and covers an area larger than the modern Great Lakes combined. The map shows the ancient shorelines of Lake Agassiz, Lake Saskatchewan, Lake Souris, Lake Dakota, and Lake Minnesota, and the present day shorelines of Lake Winnipeg, Lake Superior, and Lake Michigan.