Things to Do in Island Park, Idaho
The best things to do in Island Park, Idaho, are Harriman State Park, Big Springs and Upper Mesa Falls. Yellowstone’s west entrance is just up the highway. It’s a city of 193 people in Fremont County, spread along U.S. 20.
Island Park incorporated in 1947 and claims the longest Main Street in the world. The city is 33 miles long and about 500 feet wide in most places. At 6,359 feet, it is also the highest city in Idaho. The whole area sits inside an old volcanic caldera.
Harriman State Park
This was the Railroad Ranch, a cattle ranch and private retreat for the Harriman and Guggenheim families from 1902 to 1977. Roland and W. Averell Harriman gave it to Idaho in 1977, and it opened to the public in 1982. Today it’s 11,000 acres with more than 20 miles of trails and eight miles of the Henry’s Fork.
★ Good to know Two-thirds of the trumpeter swans that winter in the lower 48 spend the season here, and the park warns visitors to carry bear spray.
Big Springs and Johnny Sack Cabin
Big Springs pushes out more than 120 million gallons of 52-degree water a day and starts the Henry’s Fork of the Snake River. It became a National Natural Landmark in 1980. Next to it is the log cabin Johnny Sack, a German-born carpenter, built by hand in the early 1930s. He rigged a waterwheel for power.
★ Good to know Fishing isn’t allowed at the spring itself, and a half-mile accessible trail runs along it; the cabin opens to visitors June through September.
Float the Henry’s Fork
The Big Springs Water Trail is a 5-mile paddle from the springs down to Mack’s Inn. Mack’s Inn River Adventures rents rafts, kayaks, canoes, paddleboards and tubes, and shuttles you to the launch. Watch for moose, elk, eagles and swans along the banks.
★ Good to know Rentals run from Memorial Day through Labor Day.
Upper Mesa Falls
The Henry’s Fork drops 114 feet over the edge of the caldera here, in a curtain about 200 feet wide. An accessible trail and boardwalk lead to the overlooks. The visitor center is in the Big Falls Inn, built around 1915 and now on the National Register of Historic Places.
★ Good to know The visitor center normally opens in late May. The Forest Service lists it as closed for the rest of 2026, so call ahead.
Yellowstone’s west entrance
Visit Idaho puts Island Park about 20 minutes from Yellowstone’s west entrance at West Yellowstone, Montana. That makes it an easy base for day trips into the park.
★ Good to know Most Yellowstone roads close to regular cars from early November to late April; guided snowmobiles and snowcoaches run from mid-December to mid-March.
Fly fishing the Henry’s Fork
Visit Idaho calls the Henry’s Fork one of the best fly-fishing rivers in the country. Because it starts at a constant-temperature spring, it runs clear early in the season when other rivers are cold and muddy. Harriman State Park and the Last Chance area are the classic stretches.
★ Good to know TroutHunter, on the river at Last Chance, and several other fly shops in the area can set you up with flies and guides.
Henrys Lake State Park
Henrys Lake is a 6,000-acre lake at 6,470 feet, and the 585-acre state park on its shore is known for trophy trout. There’s a boat ramp, campground, hiking and biking. The park lends fishing rods if you didn’t pack one.
★ Good to know It’s open year-round, with about a dozen dry RV sites and three heated cabins in winter.
Sawtell Peak drive
A road of about 13 miles climbs 3,440 feet up Sawtell Peak, to nearly 9,900 feet. From the top you look across the caldera, Island Park Reservoir and Henrys Lake. The route passes whitebark pine and subalpine meadows.
★ Good to know July and August are best for wildflowers; the turnoff is about 1.5 miles north of Mack’s Inn.
Also in town
Island Park Reservoir, finished in 1939, for boating and fishing; Island Park Village Golf Course, 9 holes at 6,433 feet; and ATV and snowmobile rentals from Island Park Adventures and High Mountain Adventures.
How far is Island Park from Yellowstone?
About 20 minutes from the west entrance at West Yellowstone, Montana, according to Visit Idaho. Mack’s Inn, near the middle of town, is 17 miles from the entrance.
Why does Island Park have the longest Main Street?
The city runs 33 miles along U.S. 20 but is only about 500 feet wide in most places. That shape is where its claim to the longest Main Street in the world comes from.
Can you visit Upper Mesa Falls in the fall?
The visitor center usually opens at the end of May, and the Forest Service lists it as closed for the rest of 2026. Call the Ashton/Island Park Ranger District at 208-652-7442 for current road and site conditions.
Where else should I go in Idaho?
On the drive to Upper Mesa Falls you can catch glimpses of the Tetons. For more ideas, see our small towns in Idaho.
Where to find them
- Harriman State Park 3489 Green Canyon Rd, Island Park, ID 83429 Website Directions
- Big Springs and Johnny Sack Cabin Website Directions
- Mack's Inn River Adventures Website Directions
- Upper Mesa Falls Website Directions
- Yellowstone National Park West Entrance West Yellowstone, MT Website Directions
- Henrys Lake State Park 3917 E. 5100 N., Island Park, ID 83429 Website Directions
- Sawtell Peak Website Directions
Plan your trip: for events and current visitor info in Island Park, see Island Park Area Chamber of Commerce →
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Where to stay in Island Park
Keep exploring
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