Erosion is constant in Theodore Roosevelt National Park, where the colorful but crumbly Badlands are on full display. A scenic loop rings the park’s South Unit at Medora, taking visitors through prairie dog towns, river bottomland and layered bluffs. The park was established in 1947 as Theodore Roosevelt National Memorial Park, but the 21-mile loop wasn’t completed until 1968, when the final seven miles of road were laid. Visitors previously had to retrace the road from Wind Canyon and Buck Hill