Sandpoint ID to Thermopolis WY: Road Trip Guide

This 650-mile route from Sandpoint, Idaho to Thermopolis, Wyoming traverses the Bitterroot Range, the continental divide at Teton Pass (elevation 8,431 feet), and ends at the world's largest mineral hot spring in Thermopolis. The drive takes approximately 10-11 hours without stops, but plan for two days to savor the landscapes.

Few know that US-20 near West Yellowstone is part of the historic Yellowstone Highway, one of America's first transcontinental auto routes established in 1918. This road trip offers a blend of alpine lakes, volcanic plateaus, and dinosaur fossils.

The primary route uses US-95 South from Sandpoint to Coeur d'Alene, then I-90 East to Missoula, MT. From Missoula, take US-93 South to Salmon, ID, then US-28 to Dillon, MT. Continue on I-15 South to Lima, then US-20 East to West Yellowstone. Finally, US-20/26 East to Thermopolis.

• Total distance: 650 miles (1,046 km)
• Driving time: 10-11 hours, non-stop
• Best stops Sandpoint, ID to Thermopolis, WY: Coeur d'Alene, Missoula, West Yellowstone, Jackson Hole, Dubois

Fuel stations are sparse between Salmon, ID and Dillon, MT (approx. 100 miles). Fill up in Missoula or Salmon. how to find the best stops and hidden gems between cities.

Fuel and Route Economics

Gas prices vary: Idaho average $3.50/gal, Montana $3.40, Wyoming $3.30. Total fuel cost for a sedan (25 mpg) about $85. Tolls: none, but Yellowstone National Park entrance fee ($35) required if passing through; use US-20 outside the park to avoid fee.

US-93 from Missoula to Salmon is winding with narrow shoulders; watch for wildlife at dawn/dusk. I-15 through Montana is well-maintained. US-20 near West Yellowstone can have snow from October to May. Carry chains in winter.

• Infrastructure Safety & Road Quality: I-90 and I-15 are excellent; US-93 (MT) is good; US-20 east of West Yellowstone is fair with occasional frost heaves.
• Family and Child Suitability: Kid-friendly stops include the Idaho Potato Museum in Blackfoot (detour), and the National Museum of Wildlife Art in Jackson (detour).
• Pet-Friendly Framework: Most hotels in West Yellowstone and Thermopolis allow pets; rest stops with pet areas: Lost Trail Pass (MT), St. Anthony Sand Dunes (ID).
• Fatigue Management & Rest Zones: Rest areas near St. Regis (MT), Dillon (MT), and Dubois (WY). Plan to stop every 2 hours.

Hidden Off-Route Spots

Just off US-93, visit the ghost town of Cobalt, ID, accessible via a dirt road (high clearance recommended). Near Dubois, WY, the Tie Hack Historical Monument commemorates railroad tie workers. In Thermopolis, Legend Rock Petroglyph Site (30 min south) has over 300 prehistoric carvings.

The route crosses four distinct ecosystems: the pine forests of northern Idaho, the Bitterroot Valley, the Snake River Plain, and the Wyoming Basin. Near West Yellowstone, the Madison River offers world-class fly fishing. In Thermopolis, the Hot Springs State Park features free public bathing in the 104°F mineral water.

• Natural Landscapes & Attractions: Lake Coeur d'Alene, Bitterroot Mountains, Earthquake Lake (formed in 1959), Grand Teton views from US-26, Wind River Canyon
• UNESCO World Heritage Sites: Yellowstone National Park (nearby, optional detour) is a UNESCO site; the park's geothermal features are world-renowned.

Local Commerce & Culture

Missoula's downtown has craft breweries like Big Sky Brewing. In West Yellowstone, visit the Grizzly & Wolf Discovery Center. Thermopolis has the Wyoming Dinosaur Center with over 20 mounted skeletons. Local shops sell huckleberry products in Idaho and western wear in Wyoming.