Arguably, the most notable event to define Wisconsin’s geography
was the “Wisconsin Glaciation.” It radically altered the
geography of North America north of the Ohio River. It consisted
of a major advance of the North American Laurentide ice sheet,
which covered most of Canada and a large portion of the US. This
Glaciation Episode extended from about 110,000 to 10,000 years
ago. It is important to note that this was the most recent
glacial period, or said differently, the last glacial period.
The Great Lakes resulted from this episode. So did Niagara
Falls. It carved the gorge that is now the Upper Mississippi
River. One of the more incredible features of this glaciation
was that the ice sheet did not cover the entire state. In
layman’s terms, there was a large hole of geography never
covered by the ice. It is known as the Driftless Area; that is,
the glacier, when it withdrew, did not leave any drift there
because it did not cover this area. This area extended into part
of Minnesota, Iowa and Illinois as we