Cougar Mountain is one of the best-mapped trail systems in the Seattle suburbs. The great maps and trail signs make this 3,100-acre park very easy to navigate, which is convenient since this complex network is home to trail running routes of many different lengths. (Source)

The loop mapped here covers 7.6 miles of trail, but you could run for much longer if you prefer. In total, the park is home to 38 miles of hiking trails and 12 miles of equestrian trails. (Source)

To complete the loop as mapped, from the trailhead turn left on Cave Hole Trail and follow it to Old Man’s Trail, Coyote Creek Trail, and Lost Beagle Trail. Here, you’ll reach the 1,486-foot summit of the named Cougar Mountain. To complete the loop, follow Lost Beagle to Harvey Manning Trail, Cougar Pass Trail, Klondike Swamp Trail, Fred’s Railroad Trail, Shy Bear Trail, Far Country Trail, Indian Trail, and Red Town Trail.

Sources: https://rootsrated.com/stories/quick-dirty-guide-best-seattle-trail-running https://en.wikipedia.org/wiki/CougarMountainRegionalWildlandPark http://nwtrailruns.com/events/cougar-mountain-trail-run-series-1/