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Dirty Bismark



15.7 mile 25.2 kilometer loop
98% Runnable


Ascent: 970' 296 m
Descent: -970' -296 m
High: 5,960' 1,817 m
Low: 5,522' 1,683 m


Avg Grade: 2% (1°)
Max Grade: 13% (7°)


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Trail shared by Amanda Stone

A rare, long, flat-ish loop on dirt in the Front Range, named after the Morgul Bismarck road cycling route.

Amanda Stone

Features -none-

Parking fees apply at select parking lots.

Please be courteous in regards to trail closures. Large portions of this trail are clay and are therefore easily damaged while wet. Check this website for any current closures:…?


The Dirty Bismark loops takes advantage of a network of dirt trails and doubletrack in the Marshall Mesa area to make a large loop. It is mostly smooth with a couple smaller technical parts.

Need to Know

Watch out for animals on the trail - cows, prairie dogs, and rattlesnakes mostly.

Some of the parking areas require Boulder County license plates or a user fee for cars registered outside of the county.

The trail can get hot and windy as there is no tree cover. Parts of the singletrack on the west side can become very muddy with rain or snow.

This is a popular MTB route with many beginners, so try to be understanding of the many users on this trail.


You can start at the Marshall Mesa Trail as shown here, but there are numerous trailheads along the loop for access. The route description is clockwise from Marshall Mesa.

Start by heading east on Marshall Valley. You'll come to the intersection with Community Ditch, but stay straight to head east on Cowdrey Draw. You'll cross a small side road where the trail turns into Mayhoffer Singletree. Keep following the obvious route. This turns into Meadowlark. At the bottom of the hill is a small parking lot with restrooms.

From here, turn right to climb up the doubletrack Coalton. Watch for cows and prairie dogs. Coalton will take a sharp left at the top of the hill and wind back toward 128 where you'll find another small parking area. From here, the trail becomes the High Plains trail with finally some nice flowing singletrack.

At the end of this singletrack section is the Greenbelt Plateau parking area. At the parking area, turn right to follow the doubletrack up the hill. At the very end of Greenbelt Plateau you'll encounter a small rock feature and intersect with
Community Ditch. Turn left onto Community Ditch until you reach the intersection for Coal Seam. Take a hard right to follow the slightly rock Coal Seam back down to the Marshall Mesa Trail.

Flora & Fauna

Rattlesnakes, prairie dogs, yucca.

History & Background

The Morgul Bismarck is a relatively famous stage from the Red Zinger / Coors Classic road cycling race from the 1970's and 1980's. Over time, trails along the perimeter of this classic road route have been built, making the Dirty Bismarck MTB trail.

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Mar 17, 2020
Matt H
Wide open space with good views of the front range and flatirons. Mostly flat. Good for speed work.
Jul 25, 2019
Cedrick Hsin
Super fun run! — 2h 00m
Jun 6, 2019
Charles Danforth
May 18, 2019
Joe Allen
Nice trail, crowded with bikes though. 15.1mi — 2h 25m
Mar 11, 2019
Stephanie Ann
Sep 30, 2018
Alexandra Hanley
Sep 2, 2018
Caroline Jonsson
Apr 15, 2018
Ben Nissley

Trail Ratings

  3.9 from 16 votes


  3.9 from 16 votes
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in Colorado


165 Views Last Month
3,417 Since Oct 27, 2017



Looking west from the Greenbelt Plateau toward the flatirons.
Sep 24, 2017 near Superior, CO
Looking east to the sunrise along the Greenbelt Plateau Trail. July 2015.
May 3, 2017 near Superior, CO
Colorado morning sunrise from the High Plains Trail
May 4, 2015 near Superior, CO
Quarter mile into the trail headed west and looking north west toward the Flatirons.
Apr 25, 2017 near Superior, CO
Beautiful views of the front range.
May 9, 2019 near Superior, CO
The reward you get after climbing the steep hill on the Coalton Trail.
May 3, 2017 near Superior, CO


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