Great Falls to Thermopolis: A Road Trip Through Montana and Wyoming

The Pryor Mountains, visible from US-310, host one of the last free-roaming herds of wild horses in the United States. This 350-mile road trip from Great Falls, MT to Thermopolis, WY crosses the Continental Divide twice and traverses landscapes shaped by volcanic ash, glacial melt, and the erosive power of the Bighorn River. The route offers a compact yet diverse slice of the American West, from the wheat fields of central Montana to the red desert of Wyoming.

Driving time between the two cities is approximately 5.5 hours without stops, but the journey deserves at least a full day to absorb its natural and cultural offerings. Whether you're wondering how long to drive Great Falls, MT to Thermopolis, WY or seeking things to do between Great Falls, MT and Thermopolis, WY, this guide provides a comprehensive look at the route.

The primary route consists of three well-maintained highways: Interstate 15 south from Great Falls, Interstate 90 east through Billings, and US-310 south to Cody, followed by US-20 into Thermopolis. Fuel stations are plentiful in towns like Butte, Livingston, Billings, and Cody, but sparse between Cody and Thermopolis. Plan to fill up in Cody before crossing the Wind River Canyon.

• Total distance: 350 miles (563 km)
• Estimated fuel cost: $45–$60 (based on $3.50/gallon, 22 mpg)
• Best rest stop: Pompeys Pillar National Monument (mile 45 on I-90 east of Billings) – features a historic inlay and picnic area
• Road condition: Excellent asphalt on interstates; narrow two-lane on US-310 with occasional sharp curves near the Wyoming border

Fuel and Route Economics

Gas prices vary significantly along the route. Great Falls and Cody typically have lower prices ($3.40–$3.60/gallon) compared to smaller towns. Using an app like GasBuddy can save up to $8 per fill-up. For electric vehicles, charging stations are available in Billings (Tesla Supercharger) and Cody (Level 2), but none between Cody and Thermopolis – so a full charge is essential.

• Average fuel cost per mile: $0.16–$0.20
• Truck stops: Love's in Billings (I-90 exit 450), TA in Livingston
• Alternative route: Via US-212 (Beartooth Highway) adds 60 miles but offers alpine scenery – only open June–October

This route showcases three distinct ecosystems: the shortgrass prairie of central Montana, the limestone badlands of the Pryor Mountains, and the red sandstone canyons of Wyoming's Bighorn Basin. Wildlife sightings are common – pronghorn antelope, mule deer, and even the occasional black bear near the Montana-Wyoming line. The Pryor Mountains, a sky island of subalpine forest, are home to the Pryor Mountain Wild Horse Range, where about 160 wild mustangs roam freely.

• Natural Landscapes & Attractions: Pompeys Pillar National Monument (Clark's inscription), Bighorn Canyon National Recreation Area (south of Billings), Hot Springs State Park in Thermopolis (free public pool)
• UNESCO World Heritage Sites: While no UNESCO sites lie directly on the route, Yellowstone National Park (a World Heritage Site) is just 90 miles west of Cody via US-14/16. The route also passes near the path of the Lewis and Clark National Historic Trail.

Hidden Off-Route Spots

For those willing to detour 15–30 minutes, several gems await. The sandstone hoodoos of the Eye of the Needle near Lovell, WY offer a mini-Bryce Canyon experience. The ghost town of Kane, WY (abandoned rail stop) sits on the Bighorn River and provides excellent trout fishing. In Montana, the Shields River Valley (off I-90 exit 333) offers a peaceful picnic spot with views of the Crazy Mountains. For a complete list of hidden stops, see our guide on how to find the best stops and hidden gems between cities.

Local Commerce & Culture

Billings, the largest city along the route, offers a vibrant downtown with breweries, art galleries, and the Western Heritage Center. Cody, founded by Buffalo Bill Cody, is a living museum of the Old West with daily rodeos (summer) and the Buffalo Bill Center of the West. Thermopolis, named for its thermal springs, has a small-town charm with the Wyoming Dinosaur Center and a historic downtown district.

• Farmers markets: Saturdays in Billings (June–September) and Cody (July–September)
• Local specialties: Huckleberry products (jams, pies) in the Bighorn Mountains; bison burgers in Thermopolis
• Artisans: Handcrafted silver jewelry in Cody, quilt shops in Lovell

Infrastructure safety on the interstates is excellent, but US-310 between Bridger, MT and Cody, WY presents challenges: narrow lanes, no shoulders, and frequent wildlife crossings. Drive with headlights on during dusk and dawn. Cell service is spotty in the Pryor Mountains – download offline maps before leaving Billings. Climatic conditions: Summer temperatures range from 70°F in the mountains to 95°F in the Bighorn Basin; winter brings snow and ice, especially on I-90 near Livingston. The best aesthetics occur in May (wildflowers) and October (fall colors in the canyons).

• Road quality: I-15/I-90 graded A; US-310 graded B (rough patches near Wyola); US-20 graded A (new pavement)
• Fatigue management: Rest areas at mile markers 434 (I-90) and 12 (US-20); coffee shops in Greybull (US-20)
• Pet-friendly framework: Most rest stops have pet areas; hotels in Cody and Thermopolis allow dogs for a fee; keep pets leashed due to rattlesnakes (common in rocky areas)

Family and Child Suitability

The route is highly family-friendly with educational stops. Pompeys Pillar offers a junior ranger program. The Buffalo Bill Center in Cody has hands-on exhibits and a firearms museum that fascinates older kids. In Thermopolis, the Hot Springs State Park's free indoor pool is a hit for all ages. For a break, the Red Gulch Dinosaur Tracksite (near Greybull) features preserved dinosaur footprints – a 20-minute detour.

• Rest stops with playgrounds: Billings (I-90 exit 452), Cody (US-14/16 pocket park)
• Diaper-changing stations: Available at Love's in Billings, Sinclair stations in Cody
• Suggested lunch stop: The Soda Fountain in Cody – old-fashioned ice cream and sandwiches

Best Stops Great Falls, MT to Thermopolis, WY

To answer is it worth driving Great Falls, MT to Thermopolis, WY – yes, for the diversity of landscapes and the small-town experiences. For a full-day itinerary, allocate 3 hours for the Buffalo Bill Center, 1 hour at Pompeys Pillar, and 1.5 hours at Hot Springs State Park. If you have only half a day, prioritize the Wind River Canyon (south of Thermopolis) and the dinosaur museum.

• Morning: Depart Great Falls, drive to Pompeys Pillar (3h), explore for 1h
• Afternoon: Continue to Billings for lunch (30min), then drive to Cody (1h45min), spend 2h at the Center
• Evening: Drive to Thermopolis (1h15min), soak in the hot springs