By Morgan Tilton
Swaths of yellow-orange foliage. Mornings with frosted shrubs. Shorter days. These ingredients can only mean one thing: A refreshing, cooler season for trail running is here.
Pack the glove liners and windbreaker. Here are five awesome Centennial State mountain runs—plus a handful of mountain, ultra, trail (MUT) races—to add to your autumn bucket-list.

Four Pass Loop
In the heart of Colorado’s Elk Mountains, Four Pass Loop is an iconic run that traverses up-and-over four passes encompassed by the Maroon Bells-Snowmass Wilderness Area. From Maroon Snowmass Trailhead, singletrack delivers runners to Buckskin Pass, Trail Rider Pass, Frigid Air Pass, and West Maroon Pass—which each reach higher than 12,000 feet above sea level. Note: you can run the loop counterclockwise or clockwise.
Leave the trailhead at sunrise (be sure to park before 8 a.m.), pack a water filter, bring extra snacks, and plan on stopping to smell the clean mountain air.
Distance: 27.1 miles
Ascent/Descent: 7,734 feet
Boulder Skyline Traverse
Nothing compares to the ethereal glow of Boulder’s Flatirons. Quintessential to the Front Range, these giant rock fins and their surrounding ridgelines are a trail running Mecca: Why not link the most prominent summits in one go? In a stout adventure, trail runners sync up South Boulder Peak, Bear Peak, Green Mountain, Flagstaff Mountain, and Mt. Sanitas in a route known as the Boulder Skyline Traverse.
Given the traverse’s minimal shade and scarce water sources, fall season is an ideal time for the Skyline. Note: If you run the route from south to north, you can top off your water container after about 13 miles, at the Eben G. Fine Park’s drinking fountain. Purchase an annual parking permit for City of Boulder Open Space and Mountain Parks or opt for a day permit ($5) at South Mesa Trailhead.
Distance: 16.3 miles (one-way)
Ascent/Descent: 5,417 feet

Matthews/Winters Red Rocks Loop
In a perfect combo, this local loop features several zig-zagging ascents and stunning views of Red Rocks Park. The counterclockwise approach allows you a gradual one-mile warm-up before climbing to the top of the Matthews/Winters mesa. Fly down the descent, cross the highway, and settle in for an ascent to the rocky spine of Dakota Ridge. Park at Matthews/Winters Trailhead. The trail does not offer shade, so plan to the rocky spine of carry water, year-round. Tip: Tight on time? Run the 5-mile Matthews/Winters Lollipop instead.
Distance: 7 miles
Ascent/Descent: 1,293 feet
Deer Creek Canyon
An oasis in the city, this 1,634-acre park boasts 13.4 miles of trail. From Deer Creek Canyon Park Trailhead, head south on Plymouth Creek Trail—which will skirt along the southern edge of Plymouth Mountain—until you reach Homesteader Trail: a majestic section of singletrack over soft earth and beneath a forest canopy. When you reconnect with Plymouth Creek, veer west to connect with Red Mesa Loop, where you’ll have a spectacular wide-open vista on the northwest end.
Return to the trailhead via Homesteader Trail, but rather than descending Plymouth Creek Trail, go north on Meadowlark Trail, which will guide you back to the trailhead. Note: Homesteader Trail and Meadowlark Trail are bike-free zones. Love this area’s variable terrain? Check out the annual Fear the Dear 1/2-marathon race, held each spring.
Distance: 10 miles
Ascent/Descent: 2,044 feet
Turquoise Lake Trail
Flatter mountain trails are hard to find—especially with views of 14,000-foot peaks. This trail threads the eastern edge of Turquoise Lake beneath the tall umbrella of Pike and San Isabel National Forests. Run this out-and-back from south to north. Budget extra time for a stretch session at the lake’s beach.
Distance: 6.4 miles, one-way (~12.5 miles round-trip)
Ascent/Descent: 260 feet (round-trip)
Fall 2018 Trail Races
- September 22, 2018, Mountain Marmot Trail Run, Purgatory Resort, 12-mile
- September 23, 2018, Estes Trail Ascent, 4-mile or 6.75-mile
- September 23, 2018, XTERRA Golden Gate Canyon State Park trail run, 8K and 22K
- September 29, 2018, Ouray Mountain Trail Run, 12-mile
- September 29-30, 2018, The Bear Chase, 10K, 13.1-mile, 50K, 50-mile, 100K
- September 29, 2018, Suffer Better Trail Run, Evergreen, 10-mile
Know what else is going on this fall? Powder7 is giving seven pairs of skis to one person.