Parts of Roosevelt National Park at Medora ND are badlands. Closer to the Little Missouri River, the park supports a herd of bison and many wild horses. There are several prairie dog towns along the beautiful 36 mile loop road. Highly recommended if you are driving cross country. In far western North Dakota, I 94 goes within a mile of the park.
TR had a ranch here and liked to kill bison for sport. Parts of his story are touching, but not this part.