The drive at a glance

From Idaho Falls Regional Airport (IDA) to Island Park is 81 miles, about 1 hour 21 minutes by car (Rome2Rio). The route is mostly US Highway 20 north, a two-lane road through ranchland that climbs out of the Snake River plain into the Henry’s Fork Caldera.

The drive is straightforward but has a few things worth knowing about: grocery and supply stops, gas station spacing, road conditions in winter, and the photo stops worth pulling over for. This guide is the working version.

Step by step

Mile 0–28: Idaho Falls to Rexburg (~29 minutes)

From IDA, head north on I-15. Take Exit 320 to US-20. This stretch is interstate-grade highway through the Snake River plain — flat ranchland, irrigated potato fields, basalt outcrops in the distance. Limited stops.

Mile 28: Rexburg

Best opportunity for a real grocery stop. Albertsons is the easy option. Broulim’s is the larger local supermarket. Coffee, fast food, fuel. Plan 15–30 minutes for a grocery run.

Mile 28–60: Rexburg to St. Anthony to Ashton (~30 minutes)

US-20 continues north through smaller towns. St. Anthony has the closest full Broulim’s supermarket to Island Park if you skipped Rexburg. Ashton is about 33 miles south of Island Park and is the official southern entry to the Mesa Falls Scenic Byway — if you have time, the byway is an alternative scenic route into Island Park (longer, slower, but with the falls).

Mile 60–81: Ashton to Island Park (~25 minutes)

The road climbs from about 5,000 feet at Ashton up to roughly 6,300 feet at Island Park. The landscape changes from open ranchland to forest. The Henry’s Fork canyon is visible to the east in stretches. The first cabins of Island Park appear at Last Chance (mile ~75).

Practical notes

Fuel

Stations spaced reasonably until Ashton. After Ashton, the next major station is the Sinclair/Subway at Sawtelle Peak Road in Island Park. Don’t enter Island Park on a half-tank if you’re going to Yellowstone the next morning.

Cell coverage

Continuous on US-20 through Rexburg and Ashton. Spotty north of Ashton. Plan offline maps before the drive.

Winter

US-20 stays open through winter except during severe storms. Check 511.idaho.gov for conditions before leaving the airport. Carry extra blankets, water, and a phone charger in case of multi-hour weather delays.

Speed limits and enforcement

I-15 to US-20 is 75 mph; US-20 itself is 65 mph in most stretches, dropping to 35 mph through towns. Idaho State Police patrol US-20 actively, especially around St. Anthony and Ashton. Stay at the limit.

Two scenic alternates

Mesa Falls Scenic Byway (longer, more dramatic)

From Ashton, take Idaho 47 east instead of continuing on US-20. The byway adds about 30–40 minutes but includes Upper Mesa Falls (114 feet) and Lower Mesa Falls. Best on the way up if you have time the first day, or on the way out as a goodbye drive.

Continental Divide route (winter only)

Not applicable for passenger cars in winter — the high-country route between Island Park and Idaho Falls is for snowmobiles. Wheel-vehicle drivers stay on US-20 year-round.

Sources & further reading