This popular run is easily accessible from either Bozeman or Livingston. It is a mixed use trail, so be prepared to encounter other runners in addition to mountain bikers. While the climb up the mountainside isn't extremely steep, it is quite steady and relentless. The trail surface has some rocks and roots, but it's generally not very technical.
Take Exit 316 for Trail Creek off of Interstate 90. The obvious trailhead is right by the exit and has abundant parking. After parking, head up Chestnut Mountain Trail #458
. Most of the trail is on Forest Service land, but the first few miles are on private land that is open to trailusers thanks to the Gallatin Valley Land Trust and other land use advocacy groups—be respectful of the hard work these groups did to ensure public access and stay on the trails!
A little over a mile into the run, the Frog Rock Trail #463
departs to the right and contours west to an outcropping of rock that is popular with climbers. Check out the rocks if you wish, but otherwise continue uphill on the Chestnut Mountain Trail #458
as it proceeds south. You'll still be able to see Frog Rock from the trail as the rocky outcroppings are prominent and visible directly to the west. Much of the early trail passes through forested areas and the occasional meadow, which, in the summer time, are usually full of wildflowers.
As the trail climbs up the mountainside, the clearings offer increasingly expansive views of the surrounding mountains ranges. Look for the Bridger Mountains to the north, the Crazy Mountains to the northeast, and the Tobacco Root Mountains to the west. There are occasional glimpses of Interstate 90, and Bozeman is visible from higher up.
The trail continues to switchback up the mountainside for over three miles, and reaches the ridgeline at about 3.3 miles. The views open up as the trail passes through some larger clearings. Either enjoy the views and then head down for a 6.8 mile round trip run, or continue along the Chestnut Mountain Trail #458
as it follows the ridgeline for a longer outing. The summit of Chestnut Mountain is 5.2 miles from the trailhead, so running to the peak and back would be 10.4 miles roundtrip.