The West Fork San Gabriel River is a scenic waterway flowing through the rugged San Gabriel Mountains of Southern California. Originating high in the San Gabriel Wilderness, this river flows south and east for approximately 20 miles before joining the main stem of the San Gabriel River. The West Fork and its tributaries drain a significant portion of the western San Gabriel Mountains watershed.

For paddlers, the West Fork offers several distinct sections ranging from challenging wilderness runs to more accessible stretches. The upper reaches above Cogswell Reservoir provide a remote Class IV-V wilderness experience through pristine canyons, requiring advanced whitewater skills and typically only runnable during high water events. Below Cogswell Dam, a 4-mile Class III-IV section from Second Bridge to San Gabriel Reservoir offers technical pool-drop paddling. The river's flow is highly seasonal, with the best paddling typically occurring in winter and spring following significant rainfall or snowmelt. During drier months, many sections become too low for boating.

The West Fork's ecosystem supports diverse flora and fauna, including rare species like the Santa Ana sucker fish. Key landmarks include Cogswell Dam, the historic West Fork Trail, and several picturesque bridges. Primary access points are located along Highway 39 and the West Fork National Scenic Bikeway, with the city of Azusa being the nearest population center. This 6-mile paved path paralleling the lower river provides easy recreational access for hikers, cyclists, and anglers.

The West Fork holds cultural significance as part of the traditional lands of the Gabrielino-Tongva people. In the early 20th century, the area saw extensive recreational development, with resorts and camps dotting the canyon. Today, it remains a popular outdoor destination within the Angeles National Forest and San Gabriel Mountains National Monument.

Paddlers should be aware of potential flash flood dangers, especially in narrow canyon sections. A Adventure Pass is required for parking at many trailheads. While most runs are day trips, the remote upper wilderness section could potentially support multi-day expeditions for highly skilled paddlers during optimal conditions.