Dirty Bismark Route

15+ miles of dirt you can ride through most of the winter

Boulder has some pretty rich cycling heritage, reaching back to the Red Zinger / Coors Classic, a road race series of the 1970’s and 1980’s.  In its heyday this race series had several stages in Colorado, including the classic Morgul-Bismark Loop.  The Morgul Bismark was actually reborn on Memorial Day weekend 2010.

Yeah, but that’s a road ride!  What we’ve got to offer you is the Dirty Bismark, a series of trails and roads which follows the same course as the Morgul-Bismark route for 15 miles of dirty grind out on the plains.  The views are killer, and this route is a great way to get base miles on the legs during the winter months, as long as trail conditions warrant - many of these trails are a nasty muddy mess after snowmelt or heavy rain. 

We recommend starting at the Marshall Mesa Trailhead and riding the loop in the clockwise direction, so that you climb the trail-road Coalton Trail instead of using it as a descent.

Route Description

Starting from the Marshall Mesa Trailhead, you will take a left (turn east) onto the Marshall Valley Trail shortly after leaving the parking lot.  Marshall Valley is pretty flat for a while, but then crosses a bridge over a ditch and begins a short climb up to the 3-way intersection with Cowdrey Draw and Community Ditch; take a left onto Cowdrey Draw.  Enjoy this twisty, fun, descending piece of singletrack (except for annoying cow gates) as it takes you over to 66th Street.  At 66th, cross the road and get directly onto the Mayhoffer-Singletree extension trail.  This lovely stretch twists and turns as you cross water ditches and beautiful prairie - watch out for cows!  The trail crosses Coal Creek Drive and dumps you directly onto the Singletree Trail.  Follow the crusher fines Singletree until it dumps you into a neighborhood.

At this point, scant weeks ago you would have had to jump onto McCaslin Blvd for 1.75 miles of dangerous road.  Thanks to Boulder County, the ADA-accessible Meadowlark Trail now connects Singletree to Coalton!  Jump onto the Meadowlark Trail and start heading south, paralleling McCaslin, until you reach the Coalton Trailhead.

The Coalton Trail is actually a dirt road that passes under the powerlines.  A nice steady uphill on Coalton Trail gets you back on top of Marshall Mesa, and into some of the most killer views on the ride.  Follow Coalton as it turns south and takes you to a gate and trailhead at Hwy 128; here you get back onto singletrack with the High Plains Trail.  High Plains runs up and down a few drainages as it takes you back west towards Hwy 93 and Greenbelt Plateau.  When you reach the Greenbelt Plateau Trailhead (a parking lot at the corner of Hwy 128 and Hwy 93), turn right onto Greenbelt Plateau Trail - don't miss the legal singletrack running along the right-hand side of the road here!

As you crest Greenbelt Plateau and head downhill, take a righthand turn down some log stairs (ooh, getting techy!) to get over to Community Ditch.  Right before the ditch crossing are some more log stairs and some nice rocks, enjoy the one technical feature on the entire ride.  On the other side of the ditch, take Community Ditch west to the fenceline, then turn right onto Coal Seam.  This lovely twisty downhill takes you back to the Marshall Mesa Trailhead and a welcome respite from long miles.

You've completed a Boulder offroad classic - well done!

Dirty Bismark Route
Dirty Bismark Route
Click an image to enlarge.
14.80 Mi.
1522.00 Ft.
Marshall Mesa Trailhead on Google Maps
1. - Marshall Valley Trail - good
2. - Cowdrey Draw Trail - good
3. - Mayhoffer-Singletree Trail - good
4. - Meadowlark Trail - good
5. - Coalton Trail - good
6. - High Plains Trail - good
7. - Greenbelt Plateau Trail - good
8. - Community Ditch (West) - fair
9. - Coal Seam Trail - good