Guides/Overland routes/Idaho
Overland route28 midifficulty: moderate

Lemhi Pass

RegionIdahoAlso inMontanaAgencyBureau of Land Management, U.S. Forest ServiceLast verified—
Lemhi Pass — overland route near Tendoy, Idaho, Idaho
Photo by Antonia Hedrick, BLM Idaho
Trail vitals6 facts
Length
28mi
Technical difficulty
Moderate
Direction
Point to point
Vehicle
High-clearance vehicle. The road is single-lane gravel with steep grades; stock 2WD trucks handle it in dry conditions but get tested by washouts. 4WD recommended in wet conditions.
Best months
Jun, Jul, Aug, Sep
Cell coverage
None on the pass; service returns at Tendoy and Grant.
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Lemhi Pass is a 7,373-foot crossing of the Continental Divide on the Idaho-Montana border, traversed by a 28-mile gravel road between Tendoy, Idaho and the Horse Prairie Valley in Montana. The pass is the spot where Meriwether Lewis crossed the divide on August 12, 1805 — the first American to do so — and saw the Bitterroot Range stretching west. The Bureau of Land Management and Salmon-Challis National Forest manage the road jointly; Lemhi Pass was designated a National Historic Landmark in 1960.

The road is single-lane gravel with steep grades and exposed switchbacks. High-clearance 4WD is the safe call, especially in wet conditions; stock 2WD trucks manage it dry. The reliable season is mid-June through October; snow closes the upper grades the rest of the year. The Lewis and Clark Backcountry Byway designation covers the Idaho side.

Hazards

Read before you go

  • Steep, exposed Idaho-side switchbacks. Tight turns and limited shoulder.
  • Seasonal closure. Snow closes the pass October-June most years.
  • Lightning. The pass sits at 7,373 ft and draws thunderstorms in summer.
  • No services on the road. No fuel, no water, no cell coverage.
  • Wildlife. Mule deer, elk, and the occasional bear are common.
  • Single-lane sections. Pullouts are limited; meet oncoming traffic at the wide spots.
  • Bannock Pass confusion. Don't confuse Lemhi with the similarly-named Bannock Pass 33 miles south.

Location

28 mi · Overland route

Approx. location 44.974, -113.446

Trail facts

5 fields
AgencyBureau of Land Management, U.S. Forest Service
Nearest townTendoy, Idaho
Websitewww.blm.gov/visit/lemhi-pass
ClosedNov, Dec, Jan, Feb, Mar, Apr
Approx. location44.974, -113.446

Getting there

Directions

From Tendoy, Idaho (west access). From Highway 28 in Tendoy, follow signs east for Lemhi Pass / Lewis and Clark Backcountry Byway. The road climbs 12 miles to the pass.

From Grant, Montana (east access). From Montana Highway 324 in the Horse Prairie Valley, follow signs west for Lemhi Pass. The road climbs 16 miles to the pass.

Direction. Most drivers run the road west-to-east (climbing the steeper Idaho switchbacks then descending into Horse Prairie) for the Lewis and Clark historical sequence.

Photos

6 photos

Photos · 6

Field notes

Getting Oriented

Lemhi Pass crosses the Beaverhead Mountains on the Continental Divide between Salmon, Idaho (north) and Dillon, Montana (east). The standard approach from Idaho is via Highway 28 to Tendoy, then east on Lemhi Pass Road. From Montana, the approach is via Highway 324 from the Bannack/Dillon area to the Horse Prairie Valley, then west on the same road.

The Bureau of Land Management's Salmon Field Office manages the Idaho-side approach, including the Sacajawea Memorial Camp at the pass's east end on the Idaho side. The Salmon-Challis National Forest manages parts of the upper road. The pass is the highest road crossing of the Continental Divide that has a continuous historical record back to Lewis and Clark.

Trail Overview

Twenty-eight miles, point-to-point. The Idaho approach from Tendoy climbs about 1,800 feet over 12 miles to the pass at 7,373 ft. The Montana descent drops more gradually over 16 miles to the Horse Prairie Valley. The road is single-lane gravel with steep grades on both approaches; the Idaho side has the steeper switchbacks.

Most drivers run the road in two to three hours of driving plus stops. The Sacajawea Memorial Camp at the pass is the standard stop, with a small spring (Sacajawea Spring) that Lewis identified as a Missouri River headwater. The pass itself has a stone marker and long views down the Lemhi Valley to the west.

Points of Interest

  • Sacajawea Memorial Camp. BLM-developed stop just east of the pass with a small spring, picnic area, and interpretive markers.
  • Sacajawea Spring. A small flow at the camp identified by Lewis on August 12, 1805 as a most-distant Missouri River headwater.
  • Lemhi Pass marker. Stone monument on the Continental Divide at 7,373 ft.
  • Lewis and Clark Backcountry Byway. The Idaho-side designation covers the road from Highway 28 to the pass.
  • Goldstone Pass area. Forest service road network extending south from Lemhi Pass on the Idaho side, with dispersed camping.
  • Horse Prairie Valley. Cattle ranching valley on the Montana side that Lewis and Clark crossed after the pass descent.

Where to Camp

Sacajawea Memorial Camp at the pass has a small primitive camping area with vault toilets and the spring. Dispersed camping is allowed on Salmon-Challis National Forest and BLM land along the road on both sides. The Bannack State Park (a preserved 1860s mining ghost town in Montana) is 20 miles east via Highway 324 with developed camping. Lemhi or Salmon, Idaho have private RV options.

Tips for a Safe and Enjoyable Trip

  • Confirm the road is open before driving. The BLM Salmon Field Office (208-756-5400) holds current status. The road is typically passable mid-June through October.
  • The Idaho-side switchbacks are tight and exposed. Slow on descents and watch for oncoming traffic.
  • Carry water and recovery gear. There is no fuel or potable water on the road.
  • The Sacajawea Spring is the historical centerpiece. Read the Lewis and Clark journal entries before driving for context.
  • Cell coverage is gone for the entire pass. Bring an offline map.
  • Pair with the Lewis and Clark Backcountry Byway for a multi-day Lewis and Clark route through Idaho and Montana.
  • The Bannack ghost town on the Montana side is worth a half-day stop.
  • Lightning at the pass is the summer hazard; descend if storms approach.

Frequently asked

Common questions

How difficult is Lemhi Pass?
Lemhi Pass is rated moderate. The route runs 28 miles.
What kind of vehicle do you need for Lemhi Pass?
High-clearance vehicle. The road is single-lane gravel with steep grades; stock 2WD trucks handle it in dry conditions but get tested by washouts. 4WD recommended in wet conditions.
When is the best time to visit Lemhi Pass?
The best months are Jun, Jul, Aug, Sep. Avoid Nov, Dec, Jan, Feb, Mar, Apr.
Is there cell service at Lemhi Pass?
None on the pass; service returns at Tendoy and Grant.