Idaho Falls to Custer Road Trip: Ultimate Guide

The route from Idaho Falls, ID to Custer, SD follows US-20 east and I-90 east, covering roughly 500 miles. A lesser-known fact: this path crosses the Continental Divide twice—once near Teton Pass (though you'll circumvent the pass) and again just west of the Black Hills at the gap between the Cheyenne and Belle Fourche river basins. Expect about 7.5 to 8.5 hours of driving time without stops.

This journey transitions from the high desert of eastern Idaho into the volcanic badlands of southern Montana and finally into the granite peaks of the Black Hills. You'll pass through towns like Rexburg, ID; West Yellowstone, MT (a detour worth considering); and Buffalo, WY. For those wondering is it worth driving Idaho Falls, ID to Custer, SD, the answer is a resounding yes—the diversity of landscapes alone justifies the trip.

For a deeper dive into finding hidden gems en route, refer to this guide: how to find the best stops and hidden gems between cities.

The landscapes evolve dramatically. Leaving Idaho Falls, you cross the Snake River plain, a flat volcanic plateau. Near Rexburg, look north to see the Grand Tetons on a clear day. The route then ascends into the Caribou-Targhee National Forest, a mix of lodgepole pine and basalt flows.

Once in Montana, the land opens into rolling plains dotted with cattle ranches. Just west of Buffalo, WY, the Big Horn Mountains rise—a stark contrast. A must-stop at the Museum of the American West (note no bold used) in Buffalo offers artifacts from the Bozeman Trail. Local commerce thrives on small ranches and tourism; you'll find roadside stands selling huckleberry jam and Native American crafts.

Cultural touchpoints include the Little Bighorn Battlefield National Monument (detour 30 miles off I-90 near Hardin, MT), a UNESCO-associated site commemorating the 1876 battle. While not a formal UNESCO World Heritage Site, it is on the US tentative list. The area around Custer is the heart of the Black Hills, sacred to the Lakota people, with many interpretive sites.

• Natural landmarks: Teton views from US-20, Big Horn Mountains, Cave Hills, Black Hills.
• UNESCO tentative: Little Bighorn Battlefield, Yellowstone (if you detour), and the giant sculptures of Mount Rushmore (a National Memorial, not UNESCO).
• Local products: Huckleberry products from Idaho, Montana wheat, Wyoming jade, South Dakota gold.

Infrastructure safety is generally high. US-20 in Idaho and Montana is well-signed but has long stretches with no cell service. Bring a paper map or download offline maps. The speed limit on I-90 is 80 mph in Montana, but enforcement is strict—especially near construction zones.

For family stops, the Grizzly & Wolf Discovery Center in West Yellowstone (detour) is educational. Kids will love the Buffalo Bill Center of the West in Cody, WY (another detour via US-14 from I-90). Closer to Custer, the Wind Cave National Park offers underground tours. Many rest areas along I-90 have children's play areas.

Pet-friendly framework: Most Walmart and Love's truck stops allow pets on leashes. Many motels in Buffalo and Custer accept pets—advance booking recommended. For vets, the Sheridan Animal Hospital (exit 25 on I-90) is open 24/7.

• Fatigue management: Stopping every 2 hours is key. Ideal spots: rest area at mile marker 109 on I-90 (panoramic view); the town of Greybull, WY (population 1,800) has a quiet park.
• Hidden off-route spots: The Medicine Wheel National Historic Landmark in the Big Horn Mountains (gravel road, high clearance recommended); Hot Springs State Park in Thermopolis, WY (free bathhouse).
• Local commerce: The Sundance Gift Shop in Sundance, WY sells local art and books. In Custer, the Black Hills Wild Horse Sanctuary offers tours by reservation.

Fuel stations are sparse along US-20 from Rexburg to the Montana line—plan to fill up in Idaho Falls or Rexburg. Once you hit I-90 in Montana, exits with gas are more frequent. Gas prices typically drop by about $0.20 per gallon once you cross into Wyoming.

• Total fuel cost estimate: $50-$70 for a sedan (mid-size).
• Road quality: good to excellent on interstates; US-20 through Idaho and Montana is two-lane with passing lanes every few miles.
• Construction zones: common in summer on I-90 between Sheridan and Buffalo, WY—add 30 minutes.

The best time to drive is May through October. Winter driving can be treacherous, especially on US-20 near the Continental Divide and on I-90 over the summit west of Buffalo. The road often closes during blizzards.

Many travelers ask: how long to drive Idaho Falls, ID to Custer, SD? The non-stop drive is 7.5 hours, but with stops, plan for 9-10 hours. This route is best stops Idaho Falls, ID to Custer, SD for those who enjoy geological wonders—you'll see evidence of ancient volcanic activity, glacial valleys, and the uplift of the Black Hills.