Overview
Grandjean serves as the western gateway to the Sawtooth Wilderness, and the trail to Goat Lake is one of the finest objectives reachable from this trailhead hub. The 8-mile round-trip climbs through the South Fork Payette River corridor and then into the high terrain of the Sawtooth Wilderness, gaining 2,200 feet to a lake nestled among the granite spires of the range's western flank.
For hikers based in Boise or driving from the Treasure Valley, Grandjean eliminates the need to drive all the way around to Stanley. The approach to the Sawtooths from the west has a different character than the Stanley-side routes: more forested, with the river corridor providing a genuine sense of entering the mountains rather than simply arriving in them from the high valley.
Boise National Forest manages the approach corridor, and the route enters Sawtooth National Forest wilderness territory as it climbs into the high basin. The transition is marked by a wilderness boundary sign along the trail. Both forests share management responsibilities for the Sawtooth Wilderness.
The lake itself sits in a sheltered granite basin at 8,800 feet, backed by the characteristic jagged ridgeline of the Sawtooth Range. The views from the lakeshore look back down the approach drainage and west toward the Boise Mountains.
Check conditions before your visit. The Grandjean Road can be affected by late spring runoff, and the upper trail often holds snow into mid-July.
The Route
Miles 0 to 2.0: South Fork Payette River Corridor
The trail begins at the Grandjean Trailhead (approximately 5,900 feet) and follows the South Fork Payette River upstream to the northeast. The lower trail is wide and well-maintained, running through tall spruce and fir forest along the river. Water is abundant and the gradient gentle.
The wilderness boundary appears at approximately mile 1.5, marked by a wooden sign. Above the boundary, the character of the forest changes slightly: less evidence of human use, more fallen logs, a greater sense of wildness.
Miles 2.0 to 4.0: Climbing to Goat Lake
The trail steepens above mile 2 and leaves the main river corridor to climb the Goat Lake drainage. The route gains elevation through open rocky terrain with increasing views of the Sawtooth ridgeline above. Whitebark pine replaces the lower-forest species, and by mile 3.5 the terrain is clearly subalpine.
The final half-mile crosses rocky benches to reach the lake outlet. The lake basin opens suddenly, revealing the lake and the jagged peaks above in a single wide view.
When to Visit
July through September. The upper trail often holds snow into mid-July. August is the most reliable month. September is excellent for solitude and cooler temperatures.
What to Bring
Many hikers on this route carry:
- 2-3 liters of water; the river provides abundant sources in the lower section, but the upper trail relies on the lake itself
- A water filter
- Wind and rain layers
- Trekking poles for the steep upper terrain
- Sun protection for the open upper basin
Individual needs vary.
Practical Details
No permit required as of 2026. Vault toilet at the Grandjean Trailhead. Cell service absent. Dispersed camping permitted in the wilderness. Review Leave No Trace principles before camping in the lake basin.
Learn about bear canister requirements for overnight visits in this wilderness area.
Getting There
From Boise, drive north on Highway 21 to the Grandjean Road junction (approximately 70 miles). Follow Grandjean Road approximately 30 miles to the Grandjean community and trailhead. Allow approximately 2.5 hours from Boise. The Grandjean Road is primarily paved with some unpaved sections near the end.