The west end of the Gene Marshall Trail makes its way through two backcountry campsites, climbing to reach some good views to the north and west.
An Adventure Pass is required at the trailhead. There's a bar at the trailhead is now closed. Watch for ticks and poison oak.
The Gene Marshall-Piedra Blanca Trail is a National Recreation Trail, The trail can be accessed from four locations: The Piedra Blanca Trailhead at the end of Rose Valley Road, Reyes Creek Campground, Cedar Creek Trail
and the Reyes Peak Trail from Pine Mountain.
I recommend starting from the Piedra Blanca Trailhead. First cross the wide stream-bed of Sespe Creek and take the trail to the left. After 0.4 miles turn right at the junction. This will bring you through the impressive white rocks and to Piedra Blanca Camp after 2.1 miles.
A half-mile further will bring you to Twin Forks Camp, located across the creek from the trail. Continue 3.3 miles to Pine Mountain Lodge Camp; the trail is very steep in places but well worth the visit. This camp is nestled in the conifers and has a year round spring close by. From the junction at Pine Mountain Lodge Camp, the Piedra Blanca Trail continues northwest to Three Mile Camp.
The trail passes through Haddock Camp then to Bear Trap Camp , and Upper Reyes Creek Camp and finally the trail ends at the Reyes Creek Campground.The Cedar Creek Trail
(21W10) proceeds northeast from Pine Mountain Lodge to Fishbowls and Cedar Creek Camps in the Mt. Pinos Ranger District.
Another option is to start from the Reyes Creek Trail
(elev. 4000 ft., with paved parking, vault toilet and small pipe corral) at the end of Forest Service Rd. 7N11 (Camp Scheideck Rd.). The trail ascends an unnamed drainage for 2.5 miles through oak and chaparral until reaching a saddle and then descending 0.5 miles towards Reyes Creek and Upper Reyes camp (elev. 4675 ft.). This camp has 2 stoves, one on either side of the year-round creek.