North Dakota · National Park trail

Coal Vein Trail Post 3: Bentonite

in North Dakota

Notice the sediment on either side of the trail. Fifty-Five million years ago, volcanoes in the Rockies spewed out ash that blew east. At that time, this area was a vast, tropical swamp. The ash settled in wet areas and became bentonite clay.

Bentonite looks like popcorn when dry, but becomes sticky, slick mud when wet. It can absorb up to five times its weight in water. Known as the mineral of one thousand uses, it is used to seal landfills and ponds, to make cat litter, and much more.

Stay to the left to continue on the guided nature trail. Take the right on the cutoff trail to avoid a section of trail with very steep stairs. You will rejoin the guided nature trail near post #11.

States: North Dakota
Trail type: National Park trail
Centroid coords: 46.9241°, -103.3999°

About Theodore Roosevelt National Park

National Park

This trail is inside Theodore Roosevelt National Park, a national park managed by the U.S. National Park Service. Conditions, road status, trail closures, and reservation requirements are published on the park's NPS page — check it before driving in, especially in winter or during major weather events.

Entrance fee: $30 per vehicle (verify current rate on the park page). An America the Beautiful annual pass ($80) covers entrance to all NPS units.

Official NPS trail page: https://www.nps.gov/places/coal-vein-trail-post-3-bentonite.htm

Park homepage: https://www.nps.gov/thro/index.htm

Plan your hike

Practical notes

Maps + permits: long-distance trails like this often require permits for through-hiking, backcountry camping, or specific sections (especially in National Parks). Check with the maintaining organisation listed above and the relevant land manager before booking travel.

Water + supplies: water sources vary seasonally on most U.S. trails. Carry a filter and consult current trail-condition reports — through-hiker journals (PCT-L, AT Reddit, etc.) and the maintaining organisation publish regular updates.

When to go: hiking seasons vary widely with elevation, latitude, and snowpack. Through-hikers traditionally start the AT in March-April (Springer northbound) and the PCT in late April (Campo northbound). High-elevation western trails (CDT, JMT, Wonderland) generally aren't passable until July.

If you've hiked Coal Vein Trail Post 3: Bentonite and have current notes (water sources, trail closures, permit changes), tell us at /contact — we update pages as we learn.