Day 1: From Glendive, Montana; follow MT-200S, MT-200 and MT-24 (a constantly changing landscape of open prairies, dry washes and rocky crags) to Fort Peck Lake and Dam (the world's largest hydraulically earth-filled dam with a 134-mile long lake and 1,600 miles of shoreline); be sure to visit the Interpretive Center
Days 2 & 3: Follow The Montana Dinosaur Trail to see some of the most spectacular dig sites in North America 
Day 4: Visit the BLM's Missouri Breaks Interpretative Center at Fort Benton, Montana and don't miss their 30-minute video of Lewis and Clark's Corps of Discovery; follow US-89 south along Bent Creek, a beautiful stream that tumbles over boulders and fallen trees