North Dakota's Theodore Roosevelt National Park, just across Montana's eastern state line, may be the only national park in the country completely surrounded by a 7-foot fence, designed both to keep bison and feral horses inside the park, and to keep neighboring commercial livestock out.
The park is divided into three distinct and noncontiguous units: the South Unit, the North Unit, and the more remote Elkhorn Ranch Unit. Combined, the units encompass 110 square miles. Parts of the South Unit Scenic Loop Drive and North Unit Scenic Road may be closed in winter. The Little Missouri River runs through all three units.
Three visitor centers—the year-round South Unit, and the seasonal Painted Canyon and North Unit—service visitors. The South Unit's Cottonwood Campground is open all year, as is the North Unit's Juniper Campground. The South Unit's Roundup Group Horse Campground, aimed at equestrians, is open seasonally. Backcountry camping requires a free permit.
The park is host to 186 species of birds, plus bison, feral horses, elk, white-tail and mule deer, pronghorn, and prairie dogs. Geology, though, is the park's main attraction. Prairie, grasslands, juniper woodlands, floodplains and seeping springs are all represented. But the wildly eroded Badlands are the park's piece de resistance, described by Roosevelt as "so fantastically broken in form and so bizarre in color as to seem hardly properly to belong to this earth."
More than 200 fossil sites have been identified in the park, and pertified wood is common. Be aware that collecting fossils, petrified wood, and rocks in the park is illegal.
Cross country skiing and snowshoeing (on ungroomed park roads and riverbottoms) are popular ways to see the park in winter. Dark night skies and occasional northern lights make it a haven for stargazers. The changing play of light off the tortured Badland landscape is perhaps the park's most compelling single feature. Catch it at sunset if you can.