As you travel west along Interstate 90 from Billings, plan to stop off at Prairie Dog Town State Park to see the protected black-tailed prairie dog community.  These prairie dogs have great ecological significance because they create patches of habitat for a diverse number of animals, including burrowing owls, black-footed ferrets and mountain plovers.  Bring along your camera and binoculars for the best views. http://stateparks.mt.gov/greycliff-prairie-dog-town/

Spend some time in Bozeman, just a little farther west of Prairie Dog Town.  Museum of the Rockies claims the largest collection of dinosaur remains in the U.S.  You’ll see exhibits that cover more than 500 million years of physical and cultural history of the Rocky Mountains.  Displays show Native Americans, fur traders, gold seekers, and settlers.  Also included is the Tinsley House.  Costumed guides explain what life was like for the Tinsley family and others like them in the 1800s.  Nearby, you can take a raft trip on the Yellowstone River or see grizzly bears close up at the Montana Grizzly Encounter.  Choose from a number of campgrounds if you want to spend the night.  http://grizzlyencounter.org/

Leaving Bozeman, you may want to stop off at Madison Buffalo Jump State Park.  As the name implies, Native American tribes stampeded herds of bison off the cliff without the aid of horses or guns.  This practice went back about 2000 years and ended around 1750.  You’ll see high limestone bluffs and views of the Madison River. https://www.distinctlymontana.com/buffalo154

Your next stop might be Lewis and Clark Caverns State Park.  Large decorated limestone caverns are naturally air conditioned and lined with stalactites, stalagmites, columns and helictites.  You’ll also find 10 miles of hiking trails, a 40 space campground, RV dump station and all the amenities needed for your stay.  The Lewis and Clark Expedition camped within sight of the caverns in 1805, but they were not explored until 1898.  https://en.wikipedia.org/wiki/Lewis_and_Clark_Caverns