North of Ketchum and south of Stanley, the Fisher Creek / Williams Creek Loop is a popular 18 mile loop with 1,400 feet of elevation gain. The route combines paved road, dirt road and singletrack plus it offers great views of the Sawtooth range at the high points.
To reach the mountain biking trailhead from Ketchum/Sun Valley, head north on SR75 over Galena summit for roughly 50 miles. Just past Obsidian, you will drive past Fisher Creek Road. About one mile beyond, there is a road side parking area for the Williams Creek Trail.
After parking, starting riding south on SR75 for about a mile back to Fisher Creek Road. Turn left heading east on Fisher Creek Road. Continue east up this dirt road past ponds, wildlife and mountain scenery. After about six miles, there is a steep half mile climb to the summit. The road passes over the summit to the old Aztec mine. Just beyond, the singletrack begins on the left through the fence gate just past the old log buildings. After heading north on about 1.5 miles of singletrack, you'll reach the intersection with the Williams Creek Trail. Turn left heading west. After 2 miles on the Williams Creek Trail, there is another short climb. After summiting, get ready for a roller coaster ride heading back down towards SR75. After crossing a small bridge, there is a fork in the trail where you will need to stay left and ride up another small climb. The Williams Creek Trail finishes at the parking area on SR75.
Overall, Fisher Creek / Williams Creek Loop is the 21st most popular mountain bike trail of all 63 mountain biking in Idaho.