Salmon River Scenic Byway

Lost Trail Pass to Stanley

Central Idaho · Idaho · United States

Key measurements

Distance

162.3 miles

Elevation gain

5,279 ft

Elevation loss

6,056 ft

High point

7,017 ft

Low point

3,621 ft

Net change

-775 ft (7,017 ft to 6,241 ft)

Surface

Paved

Route type

point-to-point

Route Overview

This 162.3-mile route connects the timbered mountain passes of northern Lemhi County near the Montana border to the open alpine basin of Stanley. Traversing central Idaho’s rugged interior, the trip follows the North Fork and main stem of the Salmon River and cuts across the expansive high-desert valley around Salmon and Challis, and turning west on ID-75 to follow the main stem of the Salmon River through narrow granite canyons into the shadow of the Sawtooth Range. Elevation spans from a high of 7,017 feet near the northern start down to 3,621 feet near the North Fork confluence, before climbing back over 6,200 feet at Stanley.

Key Segments & Geographic Transitions

North Fork Canyon to Salmon Valley — Miles 0.0–46.9

Beginning in dense conifer forest near Gibbonsville, US-93 descends rapidly alongside the North Fork of the Salmon River. The corridor is tight and winding as it cuts through steep timbered canyon walls before merging with the main river corridor at North Fork. Continuing south, the canyon floor widens gradually, transitioning from enclosed alpine slopes into the broad agricultural rangeland surrounding the town of Salmon.

Upper Salmon River Valley — Miles 49.7–104.2

South of Salmon, US-93 traverses a high, dry valley floor flanked by the Lemhi Range to the east and the Salmon River Mountains to the west. The landscape opens into expansive sagebrush benchland with long sightlines and sweeping roadway curves. The river stays close to the highway for much of this stretch as the route approaches the junction near Challis.

Salmon River Canyon to Stanley Basin — Miles 107.7–162.3

Joining ID-75 near Challis, the road follows the main Salmon River upstream into a deep, winding river gorge. Characterized by sheer rock cliffs, river rapids, and canyon shadow, this section twists closely along the water’s edge. Near the end of the segment, the canyon walls open abruptly into the high-elevation grasslands of the Stanley Basin, framed by the Sawtooth Mountains.

Seasonal & Environmental Context

This route spans distinct microclimates. Late spring through early autumn provides the best window for transit, though high-elevation sections near Gibbonsville and Stanley can experience freezing temperatures and snow into late spring and early fall. Summer brings hot, arid weather through the lower valley sections between Salmon and Challis, while morning and evening temperatures in Stanley remain cool year-round. Thunderstorms can roll through the canyons in mid-to-late summer, causing localized runoff.

Logistics & Services

Fuel, food, and supplies are concentrated in the primary town hubs: Salmon, Challis, and Stanley. Outside these settlements, services along US-93 and ID-75 are scarce. Cell service is generally more available near the towns but intermittent to non-existent within the river canyons.

Important Considerations

Canyon walls along ID-75 and northern US-93 are subject to rockfall, particularly after rain or seasonal freeze-thaw cycles. Large game—specifically deer, elk, and bighorn sheep—frequently cross the roadway along river banks and canyon curves, especially around dawn and dusk. High winds are common across the exposed valley benches between Salmon and Challis.