Environment | Page 61

Eagle Rock at sunset

Eagle Rock at sunset, 2014. From the photograph collection of the Minnesota Department of Natural Resources.

Adult bison and calves at Blue Mounds State Park

Adult bison and calves at Blue Mounds State Park, 2007. Photograph by Wikimedia Commons user Rigadoun.

Blue Mounds State Park, named for a long, high Sioux quartzite cliff, is located in southwestern Minnesota on the Iowa and South Dakota borders. The cliff, one and one-half miles long and up to ninety feet high, appeared to be blue in color to the early Euro-American immigrants who saw it from a distance. A unique herd of bison, the largest North American mammal, makes its home in the park on 533 acres of native tall grass prairie, which escaped plowing due to poor soil quality.

Limestone seam under Stone Arch Bridge

Limestone seam under Stone Arch Bridge, 2016. Photograph by Paul Nelson.

Platteville limestone seam in Fort Snelling State Park

Platteville limestone seam in Fort Snelling State Park, 2016. Photograph by Paul Nelson.

Platteville Limestone

Platteville limestone is a distinctive building stone of southeastern Minnesota and southwestern Wisconsin characterized by its gray color, rough texture, and many fossils. It was heavily used in the early decades of the building of the Twin Cities and Faribault.