Mill Bluff State Natural Area
Notable: This geological site, tucked within Mill Bluff State Park, highlights unusual butte-like hills, pinnacles, and spires composed of Cambrian sandstone that is 490 to 543 million years old. Rising above the sandy, level bed of extinct glacial Lake Wisconsin, the formations display prominent stratification lines shaped eons ago in the shifting sands of ancient river floodplains. Several bluffs contain petroglyphs – rock carvings – dating back to the Upper Mississippian Indian culture. Vegetation on and surrounding the rock outcrops is dominated by xeric forest species, including Hillís oak, jack pine, red pine, white pine and white oak. Low blueberry, huckleberry, sweet gale, bracken fern and Pennsylvania sedge, along with prairie grasses, comprise the ground layer. The rock substrate also provides habitat for a variety of lichens, including the (barely) edible rock tripe along with colorful crustose forms.
How to get there: Within Mill Bluff State Park, Juneau and Monroe counties. From the intersection of Interstate 90/94 and Highway 12 in Camp Douglas, go west on 12 about 3 miles, then north on Highway W to the entrance to Mill Bluff State Park. Request a park map at the contact station. Hiking trails provide access to Mill Bluff and Camel's Bluff. Visit Mill Bluff for information and a map of the site. A state park admission sticker is required.