ApproachThis is one of the more direct routes to the main summit from the north. The one-way trail length is about 6 miles, elevation gain ~4200 feet. This route uses mostly steep, narrow trails instead of fire roads, by choosing Back Canyon instead of Donner Canyon on the lower part, and Bald Ridge Trail instead of Prospector's Gap Road on the upper part. The choice of Bald Ridge Trail adds about 600 feet of extra elevation gain because of its many steep climbs and drops along the route.
The trailhead is at the end of Regency Drive in Clayton. To get to Regency Drive turn off southward from Marsh Creek Road about a mile east of Downtown Clayton. Park on the road side, then walk south through a gate of Mount Diablo State Park (530').
Route DescriptionThere are three sections of this route: 1) Trailhead to Murchio Gap, 2) Murchio Gap to Prospector's Gap, 3) Prospector's Gap to main summit. The North Peak can also be reached from Prospector's Gap.
Section 1: To reach Back Canyon, take a right branch a few feet inside the gate, marked "Back Creek Road". Follow this up a gentle grassy knoll, then descend slightly into a narrow canyon by the side of a creek (Back Creek, on your right). In a mile or so the fire road becomes a narrow riparian trail. Eventually climb steeply (20+ degrees sustained slope) up many switchbacks high above the canyon, until topping out onto Meridian Ridge Road. Turn right for a few feet to find several trail junctions, this is Murchio Gap (2330').
Section 2: take narrow "Bald Ridge Trail" which is found on the left side (uphill side) of Murchio Gap and ascends steeply up the ridge. Gain glorious views on both sides: on your right is the deep Mitchell Canyon, on your left are Back and Donner Canyons and urbanized Clayton. There are three major humps on the ridge that must be climbed up and down. Then the trail traverses a dense forested slope on the left (east) side of ridge. After more roller-coaster rides the trail emerges onto Prospector's Gap Road, a few feet short of Prospector's Gap (2950'). Turn right to reach the gap, where there is a plaque about "Mining in Mount Diablo".
Section 3: Take the "Summit Trail" on the right from Prospector's Gap for the main summit, or "North Peak Road" on the left to reach North Peak. There are places along Summit Trail where one can safely scramble (class 2-3) to Devil's Pulpit (a large rock outcrop east of summit) and the summit observatory.