Portal to Porcupine

A classic Big Sky ride. 

With purpose-built flow trails (i.e., made specifically for bikers) being all the rage these days, we thought we’d throw it back to an old classic. The Gallatin Range just east of Big Sky is beautiful country, and the seat of a bike is a great way to soak it all in. —the editors

Ride Vitals
Distance: 11.6 miles
Elevation Gain: 2,050 ft.
Elevation Loss: 3,200 ft.
Ride time: 3.5 hours plus shuttle
Season: July to October
Vegetation: Pine forest, grass meadows, sage meadows
Land Management: Custer-Gallatin National Forest
Difficulty: High
Surfaces: Mostly singletrack 

A few miles of steep climbing will get you to the divide between the Portal and Porcupine drainages, then an all-singletrack, 3,000-vertical-foot descent awaits. The climb is on a wide trail, which is nice because it’s often technical and you can pick a good line. A few spots are too steep and rocky for most anyone to ride—expect to push two or three times. After riding through meadows for a bit, you might feel turned around. Don’t panic—enter the trees again and continue to Hidden Lakes trail. Almost all of the climbing is finished here—just a short descent into a rock garden and then a short climb. When you see a memorial sign on a tree, you’re at the top.

The first two miles of the descent are rocky but fun, and wind through beautiful, old forest. At one point there is a spectacular view of the Porcupine drainage and Lone Mountain. Stay focused to catch the junction at mile 8.2. If you miss this, you’ll still make it out okay, but the better way requires a right turn. After the turn, the next mile is one of the most fun and beautiful sections of trail in the Gallatin Range. The ride ends with a descent on the super buff trails of Grizzly Loop, which wind through sage hillsides with great views of Lone Mountain. 

Just past mile-marker 45 on Hwy. 191 (south of Big Sky), turn east and cross the river. Drive to the Porcupine trailhead at the end of the road. Leave a car here. Get back on Hwy. 191 and drive north to mile-marker 53 (north of Big Sky). Turn east and drive up Portal Creek Rd. Ignore fainter spur roads. After 2.9 miles, the road splits. There’s a gate (probably open) on the left road. Veer right and soon cross a bridge. A mile after this junction, there’s another junction. The left road goes to Upper Portal trailhead (Windy Pass and Golden Trout Lakes trails) and the right goes to Hidden Lakes trailhead. Park and ride to the Upper Portal trailhead from this junction. 

Bear Aware
Grizzlies are rare in Portal, but relatively common in Porcupine. Make noise and bring spray.

This article was adapted from Montana Singletrack: The Mountain Biker’s Guide to Montana, by Will Robertson. Check out beartoothpublishing.com for more guides to southwest Montana recreation.