Did you know that the four lakes of Wisconsin were created by glaciers?
Glaciers are huge sheets of ice. Madison was once covered by a glacier as tall as five Capitol buildings stacked on top of each other. Each year, the glacier moved forward, pushing tons of sand and gravel, changing the landscape as it moved.
Ice Age animals were a lot bigger. For example, large beasts like mastodons, giant beavers and the saber toothed tigers. In 20,000 B.C. Wisconsin was covered by glaciers; then, in 15,000 B.C., the glaciers began to melt. Since glaciers gave off cold air, it became very hard for trees like cattails, oak and maple to grow.
[Source: Madison City of Four Lakes]