When I was a very young boy, there were glaciers that passed through our state.
As these huge masses of ice were pushed through, they acted like large bull dozers and moved a lot of rock, dirt, and clay with them. Grinding many of the stones into small partacles. When they reached their limit and melted, they left these large deposits of rock, dirt, and clay. Some were near the sides of the glaciers, (lateral moraines) and some were near the tip of the glaciers where they ended (terminal moraines) Today these Lateral morains appear to be long narrower hills running mostly North and South. The Terminal morains are more East and West oriented. It's believed that these glaciers wore down a somewhat mountainous region into the flatter area we have now. They think that there were several passes made by glaciers, and that some parts of the state didn't get hit by all of them (the driftless area in South Western Wisconsin) The scientists all agree there were at least 3 glaciers, but others think there may have been many more.