A mere 15,000 years ago during the Ice Age, much of North America lay under a huge glacier. Mammoths, saber tooth cats and cave lions roamed the earth! Some of the best evidence of this glacier is found in Wisconsin such as the state's many lakes, river valleys, gently rolling hills, and ridges. The nearly 1,200 mile Ice Age National Scenic Trail, established in 1980, traces the glacier's edge.

...Excerpt from NPS website