West Fork of the San Gabriel River

The West Fork of the San Gabriel River is 8 miles above Azusa in the mountains. This trail is a service road that starts from the Highway 39 West Fork bridge and heads 6.5 miles west to a small campground, gaining 450 feet elevation in the process. Just past the campground, the trail rapidly becomes quite steep and eventually reaches the top of the Cogswell Dam. Several trails branch out from that point including the short Devil's Canyon segment and long continuation of this trail ending at Red Box ranger station, just South of Mount Disappointment.

Eight miles to the South of the start of the West Fork trail is the start of the main San Gabriel river trail but bicycling directly there is difficult.

NOTE: This trail was closed until recently near the 7 mile point (Cogswell Dam forest service camp entrance). This was due to the events of 2001/9/11. The trail was reopened in February 2004. Devil's Canyon is also now accessable.

The West Fork trail starts here at a bridge crossing the river. (Altitude 1590 feet) 

Kids playing in front of grafitti covered rocks near the trail head. 

The crowds and grafitti are largely gone after a mile, now just the occasional fisherman, hiker or bicyclist. 

A secluded waterfall and inviting pool about five miles from the trail start. (Altitude 2000 feet)

A tranquil stream near the Glen Trail Camp, about six miles from the trail start. (Altitude 2040 feet) 


After leaving Glen Trail Camp, the trail becomes quite steep gaining 350 feet of elevation in a little more than a half mile. Although quite scenic, the area becomes more desolate as few bicyclists and hikers travel beyond the start of the steep incline. Near the top of the trail is a heliport in the middle of nowhere. (Altitude 2300 feet)

Just past the heliport is the Cogswell Dam forest service camp. The trail was closed at this point due to the events of 2001/9/11. The trail was finally reopened at this point in February 2004.

The trail continues through a small forest service camp and then to Cogswell Dam. 

A view from the top of Cogswell Dam with the reservoir in the background. 

Bicyclists crossing the dam. 

Another view of the Cogswell reservoir. Devil's Canyon is near the upper right. 

Just above the dam, the trail splits into two different routes and both turn into dirt fire roads. The trail to the left (main trail) continues climbing for several miles, eventually connecting with the Rincon OHV trail and several other trails in the forest. The trail to the right descends a short distance to the lake. A third dirt trail starts from the far side of the dam and travels up Devils Canyon. (Altitude 2522 feet)

A scenic location along the trail. (Altitude 2640 ft)

Further up the main trail. The elevation keeps increasing (we have gained about 1200 feet from the trail head at this point) and you start to catch glimpses of the large observatory dome at Mount Wilson. At this point, the dirt trail turns back into pavement and there is a strange series of paved roads that zig-zag down to the Cogswell Reservoir lake bed. These roads were used to haul and dispose of silt from the reservoir. The Devil's Canyon trail is visible on the far side of the lake. (Altitude 2800 feet)

Another view of the strange labyrinth of roads in the middle of nowhere. Cogswell Dam is visible in the distance. 

West Fork river above Cogswell Dam. (Altitude 2900 feet)

This trail continues toward the Mount Wilson region.

Rating: * * * * *
Season: Best in spring to early summer when the stream is full and the plants colorful..
Difficulty: Easy to Glen Trail Camp, strenuous thereafter.
Hazards: No drinkable water anywhere along the trail, including the trailhead, lots of insects (in early June). Extreme isolation, once past Cogswell Dam.
More info: Field Guide, Mountain bike trails,

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Copyright 2002 by Dan Slater, All rights reserved.