Little Missouri National Grassland Bentonite Hills Trail
Martian badlands in North Dakota clay
The Bentonite Hills Trail cuts a 22-mile arc through some of North Dakota’s most otherworldly terrain, where ancient seabeds have eroded into a moonscape of clay spires and multicolored mudstone that looks more Mars than Midwest. Starting from the Burning Coal Vein parking area, the route follows old oil exploration roads through the Sentinel Butte formation, passing active paleontology sites where 65-million-year-old dinosaur bones still emerge from the bentonite clay after every thunderstorm.
Don’t let the moderate rating fool you — when wet, this bentonite clay becomes automotive quicksand that’ll bog down anything without aggressive tread and momentum. Stock high-clearance vehicles handle it fine in dry conditions, but check weather religiously and carry recovery gear. Best season runs May through October, avoiding spring mud and winter freeze-thaw cycles. The reward is absolute solitude, world-class stargazing, and geology so alien you’ll question which planet you’re actually exploring.
Trail Specs
| Difficulty | Moderate |
|---|---|
| Trail Type | Backcountry |
| Surface | Mixed |
| Features | Camping, Historic, Remote, Scenic |
| Length (miles) | 22 mi / 35.4 km |
| Duration | 1-2 days |
| Max elevation (ft) | 3200 ft |
| Best season | May-October |
| Minimum vehicle | Stock 4WD high-clearance |
| Nearest town | Medora, North Dakota |
| Land manager | Little Missouri National Grassland |
| Permit required | No |
| Cell service | None |
| Water crossings | No |
| 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 | |
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Location
Trail Conditions
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Frequently asked questions
Can a stock 4Runner or Wrangler handle this trail without modifications?
Yes, a stock 4WD high-clearance vehicle is the minimum and can complete this trail in dry conditions. The bentonite clay is the real threat — it turns into axle-deep, tire-packing grease when wet, and no amount of lift saves you from that.
What happens to the trail after rain and when is it actually drivable?
Wet bentonite clay is one of the most vehicle-immobilizing surfaces in the American West — it balls up on tires and turns slick as ice instantly. Stick to dry conditions between May and October, and if rain hits while you're out there, stop and wait it out before moving.
Do you need a permit or is there a fee to drive this trail?
No permit and no fee required — this is National Grassland managed by the USDA Forest Service, so dispersed access is free. Standard rules apply: pack out your trash, respect the land, and don't camp within a quarter mile of water sources or roads in sensitive areas.
What's the hardest section and what makes it technical?
The technical challenge isn't a single obstacle — it's the sustained clay surface across the full 22 miles, which can shift from firm to impassable within a single weather window. Loose shale sidehills and unmarked two-tracks that dead-end into ravines are the other traps that catch people off guard.
How far is the nearest gas and what should I know about cell service out there?
Medora is your last fuel stop, roughly 15-20 miles from the trailhead — fill up completely before you head out. Cell service is zero on this trail, so download offline maps before you leave and tell someone your route and expected return time.
Trail track
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