Badlands National Park, in southwest South Dakota, United States preserves 244,000 acres (98,740 ha) of sharply eroded buttes, pinnacles, and spires blended with the largest protected mixed grass prairie in the United States. The Badlands Wilderness protects 64,144 acres (25,958 ha) of the park as a designated wilderness area and is the site of the reintroduction of the black-footed ferret, the most endangered land mammal in North America.