Lonesome Highway — Centennial Mountains Divide Road to Lima via Red Rock River Valley
The divide road nobody talks about — for good reason.
The Centennial Mountains run east-west — an anomaly in the Northern Rockies — and the rough two-track that follows their crest does the same, riding the Continental Divide between Montana and Idaho with views that stretch from the Beaverhead peaks east to the Henry’s Lake basin in Idaho. The Red Rock Lakes Wildlife Refuge sprawls below the south slope, one of the last strongholds for the trumpeter swan in the lower 48. Starting near Monida off I-15 and working east toward Lima, the route climbs through aspen groves and lodgepole before breaking onto open ridgeline where the road becomes two-track rutted by elk and the occasional ranch truck. Wind is a constant — budget for being pushed around if you’re running a rooftop tent.
This is a legitimate backcountry run. Sections of the divide road are soft and rutted, and early-season snowmelt leaves the clay-heavy soils unstable well into June. Lockers help on the steeper shelf sections near Slide Mountain. The window is tight — July through September before early snow closes the higher sections. No permit required, but the Wildlife Refuge boundary limits off-road travel in the lower areas — stick to established roads. Fuel and food in Lima or Dubois, Idaho. No cell service. Carry a recovery kit, satellite communicator, and enough fuel for 100 miles of rough road. The payoff is one of the most isolated drives in the lower 48.
Trail Specs
| Difficulty | Difficult |
|---|---|
| Trail Type | Backcountry, High Clearance, Overland Route |
| Surface | Dirt, Gravel, Mixed |
| Features | Camping, High Altitude, Historic, Remote, Scenic |
| Length (miles) | 55 mi / 88.5 km |
| Duration | 1-2 days |
| Max elevation (ft) | 9400 ft |
| Best season | July-September |
| Minimum vehicle | Capable 4WD with lockers recommended |
| Nearest town | Lima, MT |
| Land manager | USDA Forest Service Beaverhead-Deerlodge National Forest / USFWS Red Rock Lakes NWR |
| Permit required | No |
| Cell service | None |
| Water crossings | Yes |
| Dispersed camping | Yes |
| Official sources | fs.usda.gov |
| Start coordinates | |
| End coordinates | |
| Copy both for Google Maps directionsClick to copy the directions URL · or open it directly in a new tab | |
| Find on Google | Search on Google → |
Location
Trail Conditions
No recent condition reports. Be the first to post one.
Log in to post a condition report.
Frequently asked questions
Can a stock Tacoma or 4Runner handle this trail, or do I need lockers?
A stock Tacoma or 4Runner can make it in dry conditions if you're a competent driver, but lockers are strongly recommended — sections along the divide get loose, off-camber, and rutted fast when wet. Don't run this in a lifted street truck or a crossover, full stop.
When does the Centennial Divide Road typically open and close each season?
July through September is your window. Snow can close the divide road well into June and return by early October at 9,400 feet. Check current conditions with the Beaverhead-Deerlodge National Forest before you go — this road doesn't get plowed and nobody's coming to pull you out.
Do I need a permit to drive this route or camp along it?
No permit is required for the Forest Service portions, and dispersed camping is allowed under standard Beaverhead-Deerlodge rules (14-day limit, 200 feet from water/roads/trails). The route passes near Red Rock Lakes National Wildlife Refuge — stay on the designated road through refuge boundaries and don't camp inside refuge land without checking current USFWS regulations.
What's the hardest section on this trail and what makes it gnarly?
The exposed ridge sections on the Centennial Divide are where things get serious — narrow two-track with steep drop-offs, loose shale, and no room to turn around if you second-guess yourself. Add in afternoon thunderstorms that roll in fast at altitude and the same sections turn into slick clay that'll slide a rig sideways without much warning.
How far is it to the nearest gas station, and is there any water on the route?
Lima, MT is your fuel stop and it's small — fill up there before you head out because there's nothing on the route for 55 miles. Water crossings exist along the Red Rock River Valley end of the route, but treat everything before drinking; carry enough stored water to cover the full day in case crossings are running high or your filter fouls.
Trail track
No GPX track for this trail yet. If you've driven it and have a track, contribute below.
Log in to contribute a GPX track.