St. George to Gardiner: Ultimate Utah-Montana Road Trip Guide

The route from St. George, UT to Gardiner, MT spans over 800 miles, crossing three states and two major mountain ranges. It takes roughly 13 hours of driving without stops, but most travelers stretch it over 2-3 days to absorb the landscapes. Historically, this corridor follows the original Oregon Trail in parts, with pioneers passing near what is now the Utah-Idaho border.

One specific fact: the section from Brigham City, UT to Pocatello, ID runs along the old California Trail, where emigrants in the 1850s faced the steep ascent of the Wasatch Mountains. Today, you'll drive I-15 north, then cut east on US-20 near Idaho Falls, finally entering Yellowstone's West Entrance (though Gardiner is the North Entrance). The route's diversity—from red rock desert to alpine forests—is unmatched.

If you're wondering how long to drive St. George, UT to Gardiner, MT, expect 12-14 hours of pure driving. To answer is it worth driving St. George, UT to Gardiner, MT, absolutely: it's one of America's great trans-Western journeys, with national parks, ghost towns, and geothermal wonders along the way.

The primary roads are I-15, US-20, and US-191. I-15 is a modern divided highway with rest stops every 30-50 miles. US-20 from Idaho Falls to West Yellowstone is a four-lane expressway with some 65 mph zones. The final leg from West Yellowstone to Gardiner along US-191 is a two-lane road winding along the Madison River, often congested with wildlife jams.

Fuel stations are abundant along I-15, but become sparse after Idaho Falls. In Yellowstone, gas is available at Mammoth Hot Springs (12 miles from Gardiner) but expensive—fill up in West Yellowstone or Gardiner. Average gas prices in 2025: $3.50/gal in Utah, $3.70 in Idaho, $3.90 in Montana.

• Best stops in St. George, UT to Gardiner, MT include: Fish Springs National Wildlife Refuge (off the beaten path), the Golden Spike National Historical Park near Brigham City, and Craters of the Moon National Monument in Idaho.
• How to find the best stops and hidden gems between cities: check out this guide on finding hidden gems.
• Things to do between St. George, UT and Gardiner, MT: hike to Timpanogos Cave near Provo, explore the lava tubes at Craters of the Moon, soak in hot springs in Ashton, ID.

Road quality on I-15 is excellent, but construction zones near Spanish Fork, UT can cause delays. US-191 in Yellowstone is narrow with limited shoulders; elk and bison crossings are common. In winter, tire chains are mandatory in some sections. Check weather at Yellowstone's road conditions page before departing.

Family-friendly stops: the Dinosaur Discovery Site in St. George (interactive fossils), the Utah Lake State Park playground in Provo, and the Idaho Falls Zoo at Tautphaus Park. Kids love the lava tubes at Craters of the Moon (bring flashlights).

Pet-friendly framework: most rest stops allow dogs on leash. National parks restrict pets on trails; in Gardiner, pet-friendly lodging includes the Yellowstone Gateway Inn. Carry a collapsible bowl and extra water.

Fatigue management: plan stops every 2 hours. Recommended rest zones: Beaver, UT (Exit 112) has a large rest area with vending machines; Malad City, ID (Exit 13) offers picnic tables; after Idaho Falls, the West Yellowstone Visitor Center has clean restrooms. Avoid driving through Yellowstone at dawn/dusk when wildlife is active.

Hidden off-route spots: take the Egin-Hamer Road near Rexburg, ID to see the St. Anthony Sand Dunes, a 10,000-acre white sand desert. Or detour 20 minutes from Gardiner to the Jardine Ghost Town, a gold mining relic from the 1890s.

The drive transitions from the Mojave Desert (St. George at 2,800 ft) to the Colorado Plateau (Zion's sister canyons near Cedar City) then climbs through the Wasatch Range (Provo Canyon at 6,000 ft). By Idaho Falls, you're on the Snake River Plain, a volcanic landscape with black lava flows. The final push enters Yellowstone's high plateau (7,500 ft) and descends to Gardiner (5,300 ft).

UNESCO World Heritage Sites en route: Yellowstone National Park (designated 1978) and Zion National Park (near St. George, a short detour). Zion's towering sandstone cliffs and Yellowstone's geothermal basins are world-class. Both are part of the larger UNESCO listing for the region.

Local commerce thrives on tourism. In St. George, buy discounted climbing gear at The Wall. In Idaho Falls, try the Snake River Winery tasting room. Gardiner's main street is lined with outfitters offering rafting and wildlife tours.