Founded in 1972, Natural Bridge State Park is a Wisconsin state park between the towns of Leland and Denzer. It is southwest of Baraboo and Devil's Lake State Park. The park is named after the largest natural arch in the state. It measures 25 feet high and 15 feet. Underneath is a rock shelter that is 60 feet wide and 30 feet deep. Native Americans used the shelter for thousands of years. The oldest remains found (charred pieces of wood) date back 10-12 thousand years old. In 1973, the arch and shelter were designated the Natural Bridge and Rockshelter State Natural Area, affording them more protection. The rockshelter was placed on the National Register of Historic Places in 1979.
During the last ice age, glaciers did not reach the area in which the park is located (these areas are called driftless areas) and therefore did not smooth out the terrain. The hills in driftless areas were created about 1.6 billion years ago and are comprised of sandstone. Over time, weather chipped away at the rock, forming the arch seen today.