THE BRIDGE: This Natural Bridge of sandstone, 35 feet high, was caved by the uneven dissolving of mineral deposits holding the sand grains together. The result after many years of erosion by water, frost action, wind, and gravity is the largest natural arch in the state. It remains today because of its location in the Driftless Area of southwestern Wisconsin, a region that was not glaciated in the last Ice Age. THE ROCKSHELTER: Beneath the Bridge is a natural rockshelter, which was excavated in 1957 by archaeologists. They discovered charred wood believed to be from the fire pits of a people here possibly as long ago as 12,000 years, making this one of the oldest dated sites for human occupancy in northeastern North America. The people of that far away time, called Paleo-Indians, may have hunted such animals as Mastodons and/or Wooly Mammoths in this area. The rockshelter at first was a seasonal and temporary refuge, later a permanent one. The Native Americans encountered here by the white settlers could be regarded as latter-day representatives of this ancient culture.