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Dirty Bismark



15.7 mile 25.3 kilometer loop
90% Singletrack


Ascent: 941' 287 m
Descent: -939' -286 m
High: 5,953' 1,814 m
Low: 5,523' 1,683 m


Avg Grade: 2% (1°)
Max Grade: 16% (9°)


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A fun Boulder area cruise following the famous Morgul Bismarck road course.

Michael Ahnemann

Electric Mountain Bikes Not Allowed

Features -none-


This ride follows the well-known Morgul Bismarck road cycling route - a famous race stage in the 70's and 80's.

The trails are easily accessible from Boulder, Superior, and neighboring towns, and it's mostly smooth with just a few slightly technical spots. It's just challenging enough to keep advanced riders interested, but rideable by just about everyone. This makes it a popular route, and it's often rideable almost all year.

Need to Know

There are several trailheads along this route, so start wherever it's convenient. You can also cross over Route 93 in a couple of places to ride more of the Marshall Mesa trail system. A great spot to do this is at the Greenbelt Plateau parking area to add on the west half of the Spring Brook Loop for an additional 8.3 miles and more singletrack.


The trail as marked here starts and ends at the Marshall Mesa trailhead, which is the largest trailhead along the trail, closest to Boulder. From the trailhead, you'll head onto the Marshall Valley Trail, which is mostly flat with a short solid-rock playground thrown in.

The trail soon crosses a bridge and meets up with Cowdrey Draw and Community Ditch trails. Take a left onto Cowdrey Draw and you'll head mostly downhill on singletrack, popping out at 66th Street.

Continue through the gate and across the road and you'll now be on the Mayhoffer-Singletree extension trail, heading towards Superior. This section twists back and forth on itself and climbs just a bit. It's a serene, rural part of the ride - you're likely to see horses or cows along the way, and it feels like you're farther away from the neighboring roads than you are.

Next you'll meet up with the Meadowlark Trail, which climbs a bit, right next to an office building. The rural feel will go away for a bit until you head away from the office building and back towards a reservoir. Then the trail heads south next to McCaslin Blvd. until you reach the Coalton Trailhead.

This section of trail (Coalton Trail) l is mostly dirt road, and it gets you to the top of Marshall Mesa. Keep going until you reach yet another small trailhead to meet up with the High Plains trail.

Follow the High Plains trail, which is singletrack with a few mildly technical rocky sections. You'll eventually reach the Greenbelt Plateau trailhead where you can either cross Route 93 to meet up with the rest of the Marshall Mesa trails, or continue along this ride back towards the start.

Continuing along this ride, you'll end up on the High Plains Trail, which is singletrack, with a few mildly technical rocky sections. From here, turn right onto Greenbelt Plateau Trail and climb this mellow, mostly smooth section of trail. After the trail starts back downhill, take a right turn over a couple of log stairs, then down a bit more to some more log stairs and a short technical rocky bit, and over a bridge to cross the irrigation ditch.

Turn left onto the Community Ditch trail heading west, and ride until you reach Route 93. Here, you have another option to cross 93 and ride the Marshall Mesa trails to the west. But to get back to the trailhead, take a right onto Coal Seam.

Coal Seam is mostly downhill back to the trailhead, and somewhat technical, with twists and turns and rocks to keep things interesting. Ride the final rock garden, or ride around it, and you'll be back where you started.

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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Jun 1, 2020
Sam Krupiarz
15.5mi — 1h 44m
May 31, 2020
Dirty with Melissa, plus some extra on the west side of 93. 21.1mi — 2h 30m
May 30, 2020
Flavio Narvaez
May 28, 2020
Jon Weaver
14.5mi — 1h 50m
May 21, 2020
Brian Carrier
Started from the Coalton Rd trailhead. Awesome ride with friends. The description "climbs for a bit by an office building" is an understatement. 15.7mi — 1h 20m
May 17, 2020
Stefano Prezioso
Started at Greenbelt Plateau Trailhead, finished at Coalton Trailhead 8.7mi
May 16, 2020
Amy Domino
May 15, 2020
Rich Guess
Learned a ton about MTB today. — 1h 32m

Trail Ratings

  3.4 from 203 votes


  3.4 from 203 votes
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1,611 Views Last Month
41,671 Since Mar 21, 2013



Beautiful evening light and views of the Flatirons and Continental Divide from the Marshall Mesa trail in South Boulder.
Nov 11, 2016 near Superior, CO
Dirty Bismarck heading towards the main parking lot.
Oct 18, 2015 near Superior, CO
Looking out to the Flatirons from the Greenbelt Plateau.
Mar 26, 2013 near Superior, CO
A short but entertaining rock playground near Marshall Mesa trailhead.
Mar 26, 2013 near Superior, CO
Small technical section on an otherwise fast trail. Beautiful views of the front range from the Dirty Bismarck.
Oct 30, 2015 near Superior, CO
Short rest for a snack and enjoy the view.
Mar 23, 2019 near Superior, CO

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