Idaho Falls to Thermopolis: Smoky Mountain Drive

Spanning approximately 250 miles, the drive from Idaho Falls, ID to Thermopolis, WY via US-20 and US-26 takes roughly 4 hours without stops. This route traverses the Snake River Plain, crosses the Continental Divide at Togwotee Pass (9,658 ft), and descends into the Wind River Valley. It passes through small towns like St. Anthony and Dubois, WY, offering a mix of volcanic landscapes, geothermal wonders, and frontier history.

One historical oddity: near the town of Shoshoni, you'll cross the "Wedding of the Waters," where the Wind River changes its name to the Bighorn River—a geographic quirk unique to Wyoming. The route also skirts the Bridger-Teton National Forest and Shoshone National Forest, providing ample opportunities for wildlife viewing.

• Total distance: ~250 miles (4 hours drive time)
• Primary highways: US-20, US-26, US-287
• Key milestones: St. Anthony, ID (30 min), Dubois, WY (2.5 hrs), Shoshoni, WY (3.5 hrs)
• Highest point: Togwotee Pass (9,658 ft)

Fuel stations are sparse between Idaho Falls and Thermopolis, especially along the remote stretches of US-26 through Wyoming. The longest gap without services is roughly 80 miles between Dubois and Shoshoni. It's wise to fill up in Idaho Falls (gas around $3.50/gal) or St. Anthony. In Wyoming, Dubois has two stations but prices can exceed $4.00/gal. Thermopolis offers competitive fuel prices near the Hot Springs State Park.

• Fuel stops: Idaho Falls (start), St. Anthony, Ashton, Dubois, Shoshoni, Thermopolis
• Recommendation: Fill up in Idaho Falls or Dubois to avoid price spikes
• Alternative fuel: No EV charging stations along route except in Idaho Falls and Thermopolis

The route showcases dramatic geological transitions. Leaving Idaho Falls, you cross the Snake River Plain, a vast basaltic lava plateau formed by the Yellowstone hotspot. The first major attraction is the St. Anthony Sand Dunes, a 10,000-acre shifting sand field popular for off-road vehicles. Further east, near Ashton, you'll find the Mesa Falls Scenic Byway (off US-20) leading to Upper and Lower Mesa Falls on the Henrys Fork of the Snake River.

As you ascend into Wyoming, the landscape changes to alpine forests and meadows of the Bridger-Teton National Forest. Togwotee Pass offers panoramic views of the Teton Range and is a prime spot for moose and elk sightings. Descending through Dubois, you enter the Wind River Valley, home to the Wind River Indian Reservation. In Shoshoni, the Wedding of the Waters site where the Wind River becomes the Bighorn River is marked by a small monument.

• Sand dunes: St. Anthony Sand Dunes (50 miles from Idaho Falls)
• Waterfalls: Mesa Falls (15 min detour from US-20)
• Pass: Togwotee Pass – highest point on route
• Monument: Wedding of the Waters near Shoshoni

Local commerce along the route is modest but authentic. In Dubois, you'll find the Dubois Museum and several gift shops selling Native American crafts from the Shoshone and Arapaho tribes. Thermopolis boasts a vibrant downtown with art galleries and the Hot Springs State Park, offering free public bathing in the state's only mineral hot springs. For a deeper dive into finding unique stops, check out how to find the best stops and hidden gems between cities.

• Museums: Dubois Museum (Wyoming history), Hot Springs County Museum
• Artisans: Beaded jewelry and dreamcatchers sold in Dubois
• Hot springs: Daily free admission at Hot Springs State Park

Road conditions vary greatly by season. In winter (November–April), Togwotee Pass can close due to snow; check WYDOT alerts. Summer brings construction zones, especially near Shoshoni. Cell service is unreliable between Ashton and Dubois (approx. 80 miles). Drive during daylight to maximize safety and views.

For family-friendly breaks, the Bear World near Rexburg, ID (20 min off route) offers drive-through wildlife viewing. In Dubois, the National Bighorn Sheep Center features interpretive displays. Thermopolis's Wyoming Dinosaur Center has life-sized skeletons and dig sites.

• Rest stops: St. Anthony Rest Area (US-20), Togwotee Pass viewpoint, Shoshoni Rest Area
• Family stops: Bear World (Rexburg), Bighorn Sheep Center (Dubois), Wyoming Dinosaur Center (Thermopolis)
• Pet stops: Hot Springs State Park has a designated pet area; many motels in Thermopolis are pet-friendly

Fatigue management: The longest stretch without services is the 80 miles between Dubois and Shoshoni. Take breaks at Togwotee Pass (scenic overlook with parking) or the Shoshoni Rest Area (restrooms and vending machines). Carry water and snacks as options are limited. The speed limit on US-26 varies from 65 mph to 70 mph; watch for wildlife at dawn and dusk.

• Break recommendations: Every 100 miles or 2 hours
• Wildlife caution: Deer, elk, and moose near dawn/dusk
• Emergency: Dial 911; next nearest services in Dubois or Thermopolis