USDA Forest Service · Idaho
Flat Rock (Idaho)
USDA Forest Service · Idaho, United States
- Sites
- 41
- Hookups
- 6 electric, 10 no hookups
- Season
- May 22 to September 15
- Max RV length
- 65 ft
- Drinking water
- Yes
- Restrooms
- Yes
- Elevation
- 6,437 ft
- Dark sky
- Bortle class 1
- Cell coverage
- AT&T weak · T-Mobile good · Verizon good (carriers' 4G LTE filings to the FCC, 2025-12; not measured here)
- Access road
- FLAT ROCK CG LOOP B (NFSR 20131-B) · crushed aggregate or gravel · moderate degree of user comfort
- Lake
- Caribou-Targhee National Forest
- Nearest town
- ISLAND PARK
- Address
- HIGHWAY 20, ISLAND PARK, ID, 83429
- Phone
- 208-558-7658 OR 208-270-0094
- Activities
- Boating, Camping, Fishing, Hiking, Hunting, Mountain Biking, Wildlife Viewing
16 numbered sites are mapped one by one - open the site map to pick yours.
About
Overview
Flat Rock Campground is located 22 miles south of West Yellowstone, Montana and 30 miles north of Ashton, Idaho in beautiful Island Park, Idaho. Flat Rock is adjacent to U.S. Highway 20 and the Henry's Fork of the Snake River at an elevation of 6,400 feet.
Recreation
Henry's Fork has great fly-fishing for rainbow and brook trout. The river's headwaters are at Big Springs, one of the nation's largest springs, just 4.5 miles from the campground. Tubing, canoeing, kayaking and rafting are also popular on the river.
The Big Springs National Recreation Water Trail begins at Big Springs and ends just northeast of the campground at Macks Inn. It offers a lazy three-hour float or canoe trip through beautiful scenery. Wildlife, including moose, bald eagles and Sandhill cranes, is often seen along the trail.
Hiking, biking, horseback riding and ATVing are popular activities. Many miles of trails crisscross Island Park, including the 2.5-mile Coffee Pot Rapids Trail, which begins at nearby Upper Coffee Pot Campground and meanders along the riverbank. The Continental Divide National Scenic Trail and the Nez Perce Trail are in the area.
Island Park Reservoir and Henry's Lake are nearby, both offer boating, water skiing and excellent fishing opportunities.
Facilities
The campground contains single and double campsites, some of which have 50-amp electric hookups. Sites are equipped with picnic and utility tables, a campfire ring and tent pad.
Vault toilets, drinking water and trash collection are provided. All interior roads and parking spurs are gravel.
Macks Inn is just across the highway from the campground and offers amenities such as boat rentals, shuttle service, showers, laundry facilities, gas and groceries.
Natural Features
Island Park is composed of two areas of extinct volcanic activity. The Henry's Fork Caldera sits inside the larger Island Park Caldera. The area is known for its dense forests of lodgepole pine, broad grassy meadows bursting with summer wildflowers and a wide variety of wildlife, including black and grizzly bears, moose, elk, deer, bald eagles, Sandhill cranes and much, much more.
A mixed growth of lodgepole pine forest provides partial shade. A portion of one loop is fairly close to the river and some sites have river views.
Nearby Attractions
Mesa Falls Scenic Byway is 11 miles south of the campground. This 28-mile road leads to scenic overlooks and trails at 110 foot Upper Mesa Falls and 85 foot Lower Mesa Falls.
Harriman State Park is 13 miles south. The Henry's Fork meanders through the Harriman, offering excellent fishing. Over 20 miles of trails are available, and wildlife is abundant in this scenic park.
Henry's Lake State Park is 10 miles north, offering fishing, a fish cleaning station and boat ramp.
Yellowstone National Park's west entrance is just 22 miles north in the town of West Yellowstone, Montana. Visitors enjoy day-tripping to the park for unparalleled wildlife viewing and the beautiful and unique scenery.
Weather, month by month
| Month | Typical high | Typical low | Coldest night | Hottest day | Years with a night below 32°F |
|---|---|---|---|---|---|
| January | 24° | 10° | -19° | 36° | 11 of 11 |
| February | 26° | 14° | -15° | 42° | 11 of 11 |
| March | 36° | 20° | 4° | 52° | 11 of 11 |
| April | 41° | 26° | 2° | 55° | 11 of 11 |
| May | 54° | 31° | 23° | 66° | 11 of 11 |
| June | 67° | 43° | 32° | 83° | 0 of 11 |
| July | 80° | 52° | 40° | 89° | 0 of 11 |
| August | 79° | 52° | 42° | 88° | 0 of 11 |
| September | 68° | 44° | 33° | 79° | 0 of 11 |
| October | 50° | 31° | 6° | 69° | 8 of 10 |
| November | 35° | 20° | -4° | 54° | 10 of 10 |
| December | 25° | 12° | -1° | 38° | 10 of 10 |
Mid-month figures from 2016–2026 of daily weather at this spot (ERA5 reanalysis via Open-Meteo, CC BY 4.0), in °F. Typical is the median; coldest and hottest are the extremes seen.
Nearby campgrounds
- Upper Coffee Pot · USDA Forest Service · 1 mi · 15 sites
- Big Springs Warming Hut · USDA Forest Service · 2 mi · 1 sites
- Mccrea Bridge · USDA Forest Service · 4 mi · 25 sites
- Big Springs Grp. Area - Island Park · USDA Forest Service · 4 mi · 1 sites
- Buffalo (Idaho) · USDA Forest Service · 5 mi · 50 sites
All public campgrounds in Idaho · Every state and province · Facts read from the operator 2026-02-25. Confirm fees, rules and current status with the operator before you go.