Rapid City to Sun Valley: Ultimate Road Trip Guide via US-14 & US-20

This 680-mile route from Rapid City, SD to Sun Valley, ID traverses four states and crosses the Continental Divide twice. The single most important detail: US-14 over the Bighorn Mountains (elevation 9,033 ft at Powder River Pass) is the fastest way to the west. Expect 12 hours pure driving, but add 2-3 days for proper exploration. The Bighorn National Forest section features the stunning Shell Creek Canyon and the historic Medicine Wheel, a 7,000-year-old Native American site.

For those wondering how to find the best stops and hidden gems between cities, this journey offers immense rewards. The best stops Rapid City, SD to Sun Valley, ID include the Little Bighorn Battlefield, Yellowstone’s Lamar Valley, and the quirky town of Dubois, WY. How long to drive Rapid City, SD to Sun Valley, ID? Without traffic, 12 hours via US-14, US-310, US-20, and ID-75. Is it worth driving Rapid City, SD to Sun Valley, ID? Absolutely—this route showcases America’s most dramatic landscapes.

Infrastructure Safety & Road Quality: US-14 over the Bighorns has 6% grades and hairpin turns (no guardrails in sections). Drive slow; watch for wildlife dawn/dusk. ID-75 near Galena Summit has steep descents. Family and Child Suitability: Yellowstone’s Old Faithful and the Grizzly & Wolf Discovery Center in West Yellowstone are hits. The Buffalo Bill Dam visitor center has interactive exhibits. Pet-Friendly Framework: Most motels in Buffalo, Cody, and West Yellowstone accept pets ($20-$50 fee). National parks allow leashed dogs on paved paths only (not backcountry). Ketchum has several pet-friendly hotels.

Fatigue Management & Rest Zones: Rest areas exist every 50-70 miles: US-14 near Dayton (mile 120), US-20 at Notch Hill (mile 480). Pull-offs in Bighorn Canyon. Pro tip: stop at the Greybull Rodeo Grounds (mile 200) for free overnight boondocking. Alternate rest at: Maverik gas stations in Buffalo and Cody – clean bathrooms and coffee. How long to drive Rapid City, SD to Sun Valley, ID? Split into three 4-hour days to appreciate the scenery.

• Day 1: Rapid City to Buffalo (168 miles) – explore Bighorns.
• Day 2: Buffalo to West Yellowstone (282 miles) – Yellowstone highlights.
• Day 3: West Yellowstone to Sun Valley (230 miles) – Teton views and Sawtooths.

Fuel stations are sparse west of Buffalo, WY, especially along US-16 towards Cody. Plan refueling at: Rapid City (mile 0), Buffalo (mile 168), Cody (mile 300), West Yellowstone (mile 450), and Idaho Falls (mile 560). Gas prices rise progressively west; expected range $3.10-$3.60 per gallon (2025). Towing or RV? Avoid US-14 over the Bighorns (narrow switchbacks). Instead, take I-90 W to I-94 W, then US-20 via Montana.

Cell coverage: AT&T and Verizon average 3G-4G in towns; dead zones in Bighorn canyon and parts of ID-75. Download offline maps. Road quality: US-14 is well-paved but winding; US-20 east of Dubois has rough patches. Two-lane highways dominate. For EV owners, Level 2 chargers in Cody and West Yellowstone; rapid charging in Idaho Falls.

Natural Landscapes & Attractions: The Bighorn Mountains offer alpine meadows and glacial cirques. Stop at the Shell Falls viewpoint (mile 150). Yellowstone’s Lamar Valley (mile 450) is prime wolf-watching territory. The Grand Tetons frame the final approach. UNESCO World Heritage Sites: Yellowstone National Park (UNESCO since 1978) is a must-stop. Climatic Conditions: Summer highs 60-80°F; July-August brings afternoon thundershowers. Winter (Oct-Apr) requires snow tires on US-14 and ID-75. Fall foliage peaks late September.

Local Commerce & Culture: Cody’s rodeo (June-August) and Buffalo Bill Center of the West anchor the region. In Dubois, the National Bighorn Sheep Center offers guided tours. Culinary Infrastructure: Grab bison burgers at the Roadhouse in Buffalo; craft beer at Melvin Brewing in Alpine, WY. For things to do between Rapid City, SD and Sun Valley, ID, visit the Hot Springs State Park in Thermopolis (free bathing) or hike the Cave Falls trail in Yellowstone’s southwest corner.

Hidden Off-Route Spots: 1) The Ghost Town of Kirwin, WY (25 miles off US-14 via muddy road) – cabins and an abandoned gold mine. 2) The Bighorn Medicine Wheel (off US-14A, requires 1.5-mile hike). 3) Harriman State Park in Idaho (elk herds and 22 miles of trails). Fuel and Route Economics: Fuel cost estimate $150-$200 for gas vehicles. Lodging midrange $120-$200/night. Park entrance fees: $35/vehicle for Yellowstone; $30 for Grand Teton. Annual pass ($80) recommended.