Deadwood to Thermopolis: Ultimate Road Trip Guide

The route from Deadwood, South Dakota, to Thermopolis, Wyoming, covers approximately 240 miles of the northern Great Plains and Black Hills foothills. You'll climb from 4,530 feet in Deadwood to over 5,700 feet near Moorcroft before descending into the Bighorn Basin at 4,300 feet. The drive takes around 4.5 hours without stops, but the best stops Deadwood, SD to Thermopolis, WY add at least two more hours. How long to drive Deadwood, SD to Thermopolis, WY? Factor in wildlife jams and photo ops. Is it worth driving Deadwood, SD to Thermopolis, WY? Absolutely—for dinosaur digs, hot springs, and frontier history.

Leaving the Black Hills, the terrain opens into rolling prairie dotted with sagebrush. As you approach the Bighorns, the landscape shifts to pine forests and granite outcroppings. The Bighorn Scenic Byway crests at Granite Pass (9,470 feet) before plunging into Wyoming's hottest valley. Local culture thrives in Cowboy bars and fossil shops. The Wyoming Dinosaur Center in Thermopolis boasts real dig sites—a UNESCO-adjacent experience (though not a listed site). Petroglyphs in the nearby Red Gulch Dinosaur Tracksite add ancient art.

• Must-see natural attraction: Medicine Lodge State Park (40 miles south of I-90)
• Local commerce: Sundance's Frontier Prison Museum, Greybull's Museum of Flight and Aerial Firefighting
• Hidden gem: Shell Falls on US-14, a 120-foot cascade

I-90 is a divided highway with a 75 mph limit; watch for deer at dawn in the Black Hills region. US-14 east of the summit has tight curves—slow to 45 mph on switchbacks. Thunderstorms pop up suddenly in summer; pull over if hail occurs. Family-friendly stops include the Spearfish City Park playground and the Hot Springs State Park in Thermopolis (free bathhouse, kids love the dinosaur statues). Pet-friendly: most rest areas have waste bins; hiking trails at Medicine Lodge allow leashed dogs.

• Safety tip: carry a paper map; GPS fails in the Bighorn canyon
• Fatigue management: rest every 2 hours at Sundance Rest Area (info booth) or Greybull City Park
• Child suitability: Dinosaur Center has interactive dig boxes; Hot Springs State Park has a kiddie pool (100°F)

For more on finding offbeat stops, check our guide on how to find the best stops and hidden gems between cities.

From Deadwood, take US-85 north to I-90, then head west through Spearfish Canyon. The interstate climbs gradually past Beulah, WY, then angles southwest on US-14 at Sundance. The final 80 miles cross the Bighorn Mountains via US-14 (Bighorn Scenic Byway). Fuel is sparse—fill up in Sundance or Moorcroft; no services for 70 miles between Shell and Dayton. Cell signal drops after Greybull.

• Key fuel stops: Sundance (Shell, Exxon), Moorcroft (Conoco), Greybull (Sinclair), Thermopolis (many)
• Peak tourist season: June–August; fall foliage in late September
• Road conditions: I-90 is well-maintained; US-14 is winding with occasional gravel patches