From its earliest known record immediately prior to the advance of the Nebraskan glacier to the present time the course of Mississippi River was affected by each advancing ice sheet in turn. The Nebraskan glacier displaced it to the east, the Kansan glacier shoved it farther east, the Illinoian glacier pushed it back west, with the retreat of the Illinoian ice it took an easterly course again, the Iowan or earliest Wisconsin glacier diverted it from one minor channel to another, the Green River lobe of the Tazewell Wisconsin ice sheet forced it back into a western course and started the Rock Island rapids, and the latest Wisconsin or Mankato invasion resulted in a great fill and the details of the course as it now is
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