FATMAP by Strava

Black Diamond Open Space

An expansive cross country-oriented trail system.

Mountain Biking Difficult

35 km
420 m
420 m
2-3 hrs
Low Point
169 m
High Point
243 m
Black Diamond Open Space Map

Mountain biking in the Pacific Northwest is renowned for its gnarly freeride lines, massive dirt jumps, and steep downhill runs. Compared to other parts of the Mountain West, it can sometimes be challenging to find good ‘ole fashioned cross country trails to ride. Black Diamond Open Space fills this void in the Seattle Area.


"BDOS offers lots of singletrack and variety, but is mostly based around XC,” according to EvergreenMTB.org. "There’s sic a few freeride and downhill trails here and in the nearby Summit Ridge & Henry's Ridge, but by NW Washington standards, BDOS is pretty flat."

This massive, complex trail system includes mile upon mile of interconnected non-motorized singletrack. In total, there are at least 64 different named trails in this trail system, plus numerous connections to other nearby trail systems.

You can easily construct a ride of any length and any difficulty in the Black Diamond Open Space—from a quick couple-mile jaunt in the woods, to this meandering 22-mile loop, or an even longer ride if you start connecting every single possible trail option that you pass. If you’re looking for a respectable pedal, try out this recommend trail combination, and then continue adding or subtracting trails from here!

Sources: https://www.evo.com/travel-guides/bike/washington/tacoma-south-puget-sound/bdos-henrys https://www.evergreenmtb.org/trails/bdos



Mostly stable trail tread with some variability featuring larger and more unavoidable obstacles that may include, but not be limited to: bigger stones, roots, steps, and narrow curves. Compared to lower intermediate, technical difficulty is more advanced and grades of slopes are steeper. Ideal for upper intermediate riders.

Medium Exposure

2 out of 4

The trail contains some obstacles such as outcroppings and rock which could cause injury.


2 out of 4

Away from help but easily accessed.

Best time to visit

between April and November


  • Flow
  • Technical
  • Singletrack
  • In the forest
  • Roots
  • Rock Gardens

Similar routes nearby

Guidebooks in this area