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Henry's Fork Caldera Trail

Targhee National Forest, Idaho · 3 min read

Distance
8.4 mi
Elevation Gain
900 ft
Difficulty
moderate
Route Type
Loop
Best Season
July through September
Est. Time
4-5 hours
Dog Friendly
Yes
Kid Friendly
Yes
Difficulty Score
6 / 10

Trailhead Amenities

Restroom
Vault Toilet
Parking
Fee Required
Cell Service
Limited
Water
At Trailhead
Camping
Developed
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Conditions, regulations, and fees change frequently. Verify with the local ranger district before your trip. Full disclaimer

At a Glance

  • Volcanic caldera rim terrain with views over the Island Park area
  • Exceptional July wildflower displays across the caldera meadows
  • Trumpeter swans and sandhill cranes in adjacent wetlands
  • Loop format through contrasting meadow and forest terrain
  • Geological story of one of North America's great volcanic systems
viewswildflowerswildlifealpine meadowrock formations

Overview

The Henry's Fork Caldera Trail in Targhee National Forest circles the rim and interior of one of North America's remarkable geological features: the caldera formed by the Yellowstone hotspot some 1.3 million years ago. Today the caldera floor is a high plateau of grassland, wetland, and lodgepole forest, providing extraordinary habitat diversity that supports an impressive array of wildlife.

The 8.4-mile loop crosses caldera meadows carpeted in July wildflowers and edges adjacent wetlands where trumpeter swans and sandhill cranes are commonly seen. The volcanic origins of the landscape are visible in the basalt outcrops and the subtle bowl of the caldera rim. Views extend west over the Snake River Plain and east toward the distant Teton peaks.

The Route

The trail begins at the Harriman State Park trailhead, which provides access to both state park and Targhee National Forest terrain. The loop heads north along the caldera rim through open meadows before descending into the interior and crossing wetland areas on boardwalk sections. The return leg passes through lodgepole pine forest on the eastern side of the loop. Trail junction signs are clear throughout.

What to Expect

The caldera meadows are exposed to afternoon wind. Bring a windbreaker even in summer. Bear activity is possible throughout this area given its proximity to Yellowstone. Carry bear spray and review proper bear awareness practices before hiking. Mosquitoes are heavy in June and early July near the wetlands.

Nearby

The Harriman Trail provides additional hiking and wildlife viewing in the same area. The town of Island Park offers lodging, restaurants, and fly fishing access on the Henry's Fork River, one of the premier trout streams in the world. Yellowstone National Park's western entrance is approximately 30 miles northeast.

Leave No Trace

This trail receives enough use that following Leave No Trace principles is important for preserving the experience for future visitors. Stay on the marked trail to prevent erosion. Pack out all waste. Avoid camping within 200 feet of water sources or the trail. Use existing fire rings only where campfires are permitted, and check current fire restrictions at checking conditions before you go before any visit. The trail and surrounding terrain remain in good condition because previous visitors have respected these norms.

Safety Considerations

The moderate rating reflects the trail's general character under typical conditions. Weather, seasonal snow, and trail conditions can change the experience significantly. Carry the 10 Essentials on any full-day outing. Inform someone of your plans and expected return time before heading out, particularly on longer or more remote trails. Cell service varies throughout Targhee National Forest and may be unreliable in canyon bottoms or remote terrain.

Trailhead Parking

Harriman State Park trailhead off US-20 northwest of Island Park. Paved lot with fee station. Day use fee applies (as of 2026).

← Back to Targhee National Forest

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Frequently Asked Questions

What is the Henry's Fork Caldera?
The Henry's Fork Caldera is a 23-mile-wide volcanic caldera formed approximately 1.3 million years ago as part of the Yellowstone hotspot system. The caldera floor is now a high plateau supporting forests, wetlands, and meadows. It is distinct from the Yellowstone caldera to the northeast.
How difficult is the Henry's Fork Caldera Trail?
The 8.4-mile loop is rated moderate with 900 feet of cumulative elevation gain. The terrain is generally rolling with no sustained steep sections. Most hikers complete the loop in 4 to 5 hours.
What wildlife can I expect to see?
The caldera's wetlands support trumpeter swans, sandhill cranes, osprey, and great blue herons. Bison from nearby Yellowstone occasionally range into this area. Moose use the willow thickets year-round.
When does this trail open?
The caldera meadows are accessible by early July in most years. Spring snowmelt creates saturated soils through June. The trail is typically open through early October before winter snowpack arrives.