Between Troy and Libby in the Kootenai National Forest, the Skyline National Recreation Trail (#13) is open to mountain biking and rolls along a series of peaks over 15+ miles in the Purcell Mountains until dropping down to the Yaak River.
The southern trailhead is on FS399 off FS600 near Libby, while the northern trailhead is on the Yaak River along SR508 near FS471 north of Troy.
To reach the mountain biking trailhead from Libby, turn onto Highway 37 and turn left onto River Road. Drive about 4 miles, turning right onto Quartz Creek Road 600, Drive 5 miles and just after crossing Quartz Creek bridge, take the right fork onto Ransome Creek 4654. After 7 miles, turn onto the C Spur of Road 4654. Follow for approximately .5 mile.
Overall, Skyline National Recreation Trail is the 27th most popular mountain bike trail of all 32 mountain biking rides in Montana.