The park's South Unit lies alongside Interstate 94 near Medora, North Dakota. The North Unit is situated about 80 mi (130 km) north of the south unit, on U.S. Highway 85, just south of Watford City, North Dakota. Roosevelt's Elkhorn Ranch is located between the North and South units, approximately 20 mi (32 km) west of US 85 and Fairfield, North Dakota. The entire park is contained within the Little Missouri National Grassland, and the Little Missouri River flows through the park. The Maah Daah Hey Trail connects all three units.
In 1884, after the death of his wife and mother (on the same day), Roosevelt travelled to his North Dakota ranch to rebuild his life and to recover from the tragedy. The badlands were a catharsis for him and although he returned east several times, for most of two years he ranched in the area and noted his experiences in pieces published in eastern newspapers and magazines. Returning east and back into politics, Roosevelt would forever associate himself with the vanishing frontier and the life of the western cowboy and rancher.
The park displays spectacular seasonal variations in scenery. Sprouting plants and moisture in the spring accentuates stria of green, blue, red and white. Red "clinker" (a naturally baked rock locally known as "scoria") dominates in the summer and golden brown grasslands in the fall. Winter is almost devoid of color and the landscape is often covered with a thin layer of snow.
The park is well suited to back country hikers and permits can be obtained at either park office. It is possible to hike for days without seeing or hearing another human or evidence of development. The park units are mostly surrounded by Forest Service grasslands. Sagebrush grows throughout most of the park. The area has very dark skies with excellent star gazing and northern lights displays. However, the conditions are harsh, with little or no natural water, and summer temperatures can stay above 95°F (35°C) and winter temperatures below -20°F (-30°C) for extended periods. The bison can be very dangerous, especially during springtime calving. They have been known to destroy automobiles when drivers get too close.
A large variety of wild animals can be spotted, including; buffalo (bison), elk, pronghorn, prairie dogs, coyotes, wild horses, Bighorn sheep, wild turkey, rattlesnakes, and blacksnakes. Bison and Bighorn sheep were reintroduced into the South unit in 1956, some 75 years after they had been extirpated.
The entire park has been surrounded with a tall woven wire fence to keep bison separated from commercial livestock. The North Unit was fenced by 1962 when bison were reintroduced there. The park has a capacity for about 500 bison and relies on roundups to keep their population below this number. Captured bison are sold or go to other parks or to Native Americans. Wild horses are kept to a level of about 100 in the park through occasional roundups.
Roosevelt's Elkhorn Ranch is a remote and seldom-visited area of the park not easily accessible by vehicle. The most direct route to the ranch is via US 85 at Fairfield. A system of gravel roads leads approximately west to the Little Missouri River. Once visitors reach the river, it must be forded (on foot or possibly 4x4, depending on the river's depth). The actual ranch is a one-mile (1.6 km) hike beyond the river. A visitor's log at the trailhead revealed fewer than 20 visitors in the year preceding July 2006. Today almost nothing is left of the ranch. The outlines of the former buildings are surrounded by fences, but even the foundations are gone. With the exception of a National Park Service map and tack board, the site has probably changed very little since Roosevelt's days.