Lonesome Highway — Centennial Road to Challis via the Lost River Valley Desert Floor
Idaho's emptiest valley under its highest peaks.
The Lost River Range holds Idaho’s highest summit, Borah Peak at 12,662 feet, and the wide desert floor running beneath its east face is one of the least-trafficked overland corridors in the northern Rockies. This route picks up from Mackay and follows the valley north through sagebrush flats and dry washes, past the 1983 Borah Peak earthquake scarp — still a raw, fractured line across the desert — before curving into the Pahsimeroi Valley and dropping toward Challis along the Salmon River. The road surface is mostly graded dirt and gravel with washboarded stretches and occasional sandy washes that demand attention at speed. The scale out here is disorienting: the peaks above you are genuinely 8,000 feet taller than where you’re driving.
Moderate difficulty — stock high-clearance 4×4 handles it fine in dry conditions, and most of the route is passable for capable 2WD when graded. The real challenge is logistics: this is remote, and it means it. Fuel in Mackay before heading north; the next reliable pump is Challis, roughly 60 miles out. No permit required. Best season is June through October; spring runoff can wash out low-water crossings. Dispersed camping is wide open in the BLM corridor flanking the valley. Cell service is essentially nonexistent between the two towns.
Trail Specs
| Difficulty | Moderate |
|---|---|
| Trail Type | High Clearance, Overland Route |
| Surface | Dirt, Gravel, Sand |
| Features | Camping, Historic, Remote, Scenic |
| Length (miles) | 62 mi / 99.8 km |
| Duration | 1-2 days |
| Max elevation (ft) | 6300 ft |
| Best season | June-October |
| Minimum vehicle | High-clearance 4x4 recommended |
| Nearest town | Mackay, ID |
| Land manager | BLM Challis Field Office / USDA Forest Service Salmon-Challis National Forest |
| Permit required | No |
| Cell service | None |
| Water crossings | Yes |
| Dispersed camping | Yes |
| Official sources | BLM Challis Field Office Salmon-Challis National Forest |
| Start coordinates | |
| End coordinates | |
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Location
Trail Conditions
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Frequently asked questions
Can a stock Tacoma or 4Runner handle this route without modifications?
Yes, a stock high-clearance 4x4 like a Tacoma or 4Runner handles this fine under normal conditions. The 62-mile run is moderate with sand and gravel — not technical rock crawling. Aired-down tires help in the sandy sections.
When does this route typically close and when does it open back up?
Best window is June through October. Spring mud and potential snow close sections of the valley floor, and early season can leave the dirt surface badly rutted. Don't push it before late May unless you've confirmed conditions locally.
Do I need a permit to drive or camp along this route?
No permit required to drive the route. Dispersed camping on BLM land is free and legal with standard 14-day stay limits. Check with the BLM Challis Field Office for any fire restrictions, which are common mid-summer in this region.
What's the hardest section and what should I actually expect?
There's no single brutal obstacle — the challenge is cumulative: soft sand, washboard gravel, and occasional water crossings with zero infrastructure and zero cell service for the full 62 miles. If something breaks, you're solving it yourself or waiting a long time for help.
How far is it between fuel stops, and is there water available on the route?
Fuel up in Mackay before you start — it's roughly 100 miles of remote driving before you reach Challis, and there's nothing in between. There are water crossings but treat all water before drinking; no potable water sources exist along the valley floor.
Trail track
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