Many backcountry trails are open to those on horseback, and you can use either your own horse or go on a guided trail ride with a park concessionaire. In the South Unit, contact Peaceful Valley Ranch, P.O. Box 308, Medora, ND 58645 (tel. 701/623-4568). They operate from Memorial Day to Labor Day and have regularly scheduled horseback rides lasting from 1 1/2 to 5 hours. Trail rides run daily from 8:30am to evening, and all scheduled rides include a riding lesson. An overnight ride to Diamond Bar Bed and Breakfast can be arranged. In the North Unit, the concessionaire is Little Knife Outfitters, Box 82, Watford City, ND 58854 (tel. 800/438-6905 or 701/842-2631; www.littleknifeoutfitters.com).