I believe there are 3 units, North, South and Elkhorn Ranch unit. We stayed at the Red Trail CG in Medora ND. It allowed walking to the heart of Medora which was a nice town with history to enjoy. Medora is the South Unit Visitor Center off I94. The North Unit Visitor Center is on Hwy 85. At night in Medora at the Burning Hills Outdoor Theater is a great show. You can find the theater website with a gsearch. Next to the theater is a restaurant Pitchfork Steak Fondue. While we did not go there the night of our show, the place was very busy. There is additional interesting museums to visit in Medora, again easy walking. Out in the badlands area there are plenty of bison, prairie dogs estates and sightings of elk. The Elkhorn Ranch was Teddy Roosevelt's ranch. The sight remains, but not the ranch. Finally your first exposure going West on I94 will be the Painted Canyon Visitor Center. There you will be able to avail yourself of further info to the area you are interested in. Attached is the NPS info on the NP. You will really enjoy this area.
http://www.nps.gov/thro/parknews/loa...&pageid=416286