The Midwest is defined by some of the greatest natural features of North America. To the west lie the Great Plains, to the east the Appalachian Mountains. The Midwest’s southern boundaries are formed roughly by the Ohio and the lower Missouri Rivers. To the north lie the Great Lakes. Through the Midwest flows the continent’s greatest river, the Mississippi.

This landscape was carved chiefly by glacial advances and retreats. The last advance, the Wisconsinan, named after the state where glacial deposits were first identified, covered roughly the north half of the Midwest—almost all of Michigan and Minnesota, most of Wisconsin, and some of Ohio, Indiana, Illinois and Iowa. next >>

The glaciers began retreating around 18,000 years ago, leaving behind a landscape of rolling hills and plains in its melting wake. The environment was unlike any today.

Northern Ohio, Indiana, and Illinois were flat lowlands, and the floor of the Great Lakes was higher. Farther south, the Appalachian Plateau reached into southeastern Ohio. << back