Granite rock outcrops along the Upper Minnesota River are among the oldest exposed rock in North America, dating back approximately 3.6 billion years. These outcrops are also home to rare and specialized plant and animal communities rarely found elsewhere in Minnesota, including several types of cactus and one of Minnesota's only three lizard species, the five-lined skink. However, these rock outcrops are increasingly threatened by mining, overgrazing, and development.
