The eastern foothills of Mount Diablo are one of the most attractive parts of Mount Diablo State Park. The partially-wooded, grassy hills in this quiet, isolated corner of the park are more typical of the East Bay than the chaparral-dominated slopes of the mountain.
This very scenic loop starts on a ranch road just outside Morgan Territory. Cutting through Morgan Territory and entering Mount Diablo State park, the route climbs through the picturesque Riggs Canyon, ending up on a high ridge with superb views of endless rolling hills. It then descends through dense woodland. There’s a nice mixture of grassland and forest and the trails, although not deserted, are little-used. Aside from the suburban road at the beginning of the hike, there’s no sign of development anywhere along the hike, and the entire area is very quiet. Most visitors are mountain bikers.
One of the best things about this hike is that no part of it is grazed by cows. The roads and the surrounding grasslands don’t have the worn-out look that heavy grazing produces, and there’s no cow manure on the roads (although there’s sometimes horse manure). Overall this is a very enjoyable and satisfying hike.
Start on Finley Road. There’s no parking at the trailhead, so you have to park about a half-mile down the road, on a wide dirt shoulder at a bend in the road under some huge oak trees. The pullout is unmarked but it’s usually easy to find, since on weekends there are always other cars parked there.
Walk up the road, which is pretty scenic. Although it’s a dead-end road it still seems to be fairly busy. At the end of the public road there’s a trailhead with a big sign and free maps. Oddly, a trail begins here, but after running alongside the road for a few yards it just dumps you back on the road.
After another few minutes on the paved road, a dirt road appears to the left. This is where the real trail starts. The road climbs gently, entering a shady grove. and later passing an old deserted white house.
You can, optionally, take a side trip on the Walnut and Amphitheater Trails. The scenery isn’t anything special until the very end, where the trail passes through an attractive meadow dotted with rock formations and oaks. This is the amphitheater; it’s a sort of terrace surrounded by high rocky cliffs. It might be a nice place to have lunch since you can sit on the rocks.
As Finley Road continues to climb, it opens up, with woodland giving was to open grassland, and with increasingly scenic views. Turn onto Highland Ridge Road, which continues to climb, becoming progressively steeper and also more scenic as it enters a patchy oak grove near the high point of the hike. The views from Highland Ridge Road and the Tassajara Creek Trail are really the highlight of the hike.
The climb seems like it will go on forever, but finally the Tassajara Creek Trail branches off to the left. This is the high point of the hike.
The Tassajara Creek Trail starts out more or less level, meandering along a scenic, partially-wooded hillside. The trail mostly passes through open grassland, but there are also some patches of woodland with some really big trees. Ignore the prominent dirt road that branches off to the left and continue along the trail, which can be somewhat rough.
There’s a picnic table at Bob’s Pond.
The trail descends through a wooded canyon. The woods aren’t especially attractive; they’re kind of dense, with small trees. There’s a lot of poison oak along the trail. Fortunately the trail is in good enough condition that you can easily avoid the poison oak, but you have to constantly watch out for it.
Near the top of the woods there’s an unofficial trail to the right. Near the bottom there’s a second unofficial trail to the right, which is just as wide and well-established as the actual trail. Take this trail. After just a few yards it ends at Riggs Canyon Road. Turn left onto the road.
Riggs Canyon Road descends through the dense woodland at the bottom of the canyon. It’s more attractive than the Tassajara Creek Trail. It’s much easier going than the trail; there’s still a lot of poison oak but it’s not a problem since the road is so wide.
There’s a slight climb as Riggs Canyon Road rejoins Old Finley Road. Take the road back to the parking area on Finley Road.
© 2015 David Baselt
Re-hiked 2020, no changes