Thermopolis to Keystone: Ultimate Road Trip Guide

This drive traces the edge of the Great Plains, cutting through the Bighorn Basin and the Black Hills, with 380 miles of varied terrain that shifts from high desert to pine forest.

You'll cross the Continental Divide twice, pass through the historic towns of Buffalo and Gillette, and end near the granite peaks of Mount Rushmore. The route is a microcosm of the American West, where dinosaur bones, gold rush history, and cowboy culture converge.

Before you set out, remember that this is a journey of about 6.5 hours of pure driving, but the real value lies in the detours and discoveries along the way. For strategies on uncovering the best stops, check out how to find the best stops and hidden gems between cities.

Infrastructure Safety & Road Quality

The interstates are in excellent condition, but sections of US-20 are two-lane with sharp curves; take it slow through the Bighorn canyon. In winter, expect snow and ice – always check road conditions.

Cell service is spotty in rural areas, so download offline maps. Carry a physical map as backup.

Family and Child Suitability

• Thermopolis offers a dinosaur museum and hot springs pool.
• Devils Tower has a visitor center with junior ranger program.
• Keystone's Mount Rushmore has interactive exhibits and an evening lighting ceremony.
• Plan rest stops every 2 hours; many towns have parks or fast food.

Pet-Friendly Framework

Most roadside parks and rest areas allow pets on leashes. Many hotels in Buffalo and Keystone are pet-friendly, but confirm in advance. National monuments like Devils Tower permit dogs on trails, but not in buildings.

Culinary Infrastructure

Along the route, you'll find classic western steakhouses, such as the Historic Sheridan Inn, along with fast-food chains at every town. For a picnic, stock up at grocery stores in Buffalo or Gillette.

Climate and Route Aesthetics

Expect hot summers (90°F+) and cold winters (often below freezing). The aesthetic shifts from stark red rock to golden plains to verdant forest, peaking in autumn when the aspens turn gold.

Fatigue Management & Rest Zones

Designated rest areas exist at mile markers 40 and 150 on I-25, and on I-90 near Sundance, WY. Take advantage of these for quick naps or leg stretches. If you feel drowsy, stop in a town like Buffalo or Newcastle to get a coffee.

Natural Landscapes & Attractions

The route passes through three distinct ecosystems: the red desert of the Bighorn Basin, the rolling plains of northern Wyoming, and the Ponderosa pine forests of the Black Hills. Each offers unique geological and scenic highlights.

• Thermopolis Hot Springs State Park – mineral waters at 104°F.
• Boysen State Park – a reservoir with camping and boating.
• The Bighorn Mountains – crossing via US-16 offers panoramic views.
• Devils Tower National Monument – a 40-mile detour from Moorcroft.
• Badlands National Park – 80 miles south of Keystone, worth the extra drive.

UNESCO World Heritage Sites

While this route has no UNESCO sites itself, it's a short drive from Yellowstone and Grand Teton (World Heritage) to the west. In the Black Hills, nearby Mount Rushmore is a National Memorial but not a UNESCO site. However, the nearby site of the Wounded Knee Massacre is on the National Register, and the region's cultural history is rich.

Local Commerce & Culture

Buffalo, WY, is a classic western town with a historic Main Street and the Occidental Hotel, once frequented by Buffalo Bill. Gillette, WY, is a coal-mining hub with a modern energy museum. In Keystone, souvenir shops line the main drag, but for authentic local flavor, stop at a small-town diner like the Chuckwagon in Custer.

Hidden Off-Route Spots

For a quiet picnic, detour to Keyhole State Park near Moorcroft, popular for fishing and birdwatching. Another gem: the tiny town of Ten Sleep, WY, named for the distance between resting points on the old wagon trail. Its canyon offers climbing and solitude.

Driving Time and Route

How long to drive Thermopolis, WY to Keystone, SD? Typically 6 hours 20 minutes without stops, but plan for 8–9 hours with breaks. The fastest route follows US-20 east to I-25 north, then I-90 east.

Key highway segments: US-20 through the Bighorn Basin, I-25 from Buffalo to Sheridan, and I-90 from Sheridan to Rapid City. All are well-maintained, with speed limits of 70–80 mph on interstates.

Traffic is generally light, but watch for livestock and wildlife, especially at dawn and dusk.

Fuel and Route Economics

• Gas prices drop significantly once you cross into South Dakota; fill up in Gillette or Moorcroft.
• Total fuel cost for the trip: about $50–$70 depending on your vehicle.
• No tolls on this route.
• Food and lodging range from budget to moderate; Buffalo and Gillette offer the most options.