officially known as the East Fork. Here it turns abruptly south, flowing through a steep, rugged canyon. It is joined from the east by the Fish Fork, which originates on the northwest slopes of Mount Baldy. Below the Fish Fork the East Fork flows through the "Narrows", one of the deepest gorges in Southern California. From the floor of the canyon at , Iron Mountain rises to the southeast, while Mount Hawkins, , rises to the northwest. The Iron Fork tributary joins from the west roughly in the middle of the Narrows. Near the lower end of the Narrows, the river passes under the Bridge to Nowhere, a high arch bridge that was abandoned after the huge flood of 1938 washed out a highway under construction along the East Fork. The bridge remains today as a popular destination for hikers and bungee jumpers. After emerging from the Narrows the river continues flowing south through a somewhat more open valley, receiving several tributaries including Devil Gulch and Allison Gulch, before reaching Heaton Flat, a popular trailhead and the end of the East Fork Road, which parallels the lower section of the river. The river receives Cattle Canyon, its biggest tributary and then turns sharply west, flowing past the Camp Williams Resort and a number of U.S. Forest Service and Los Angeles County fire fighting facilities, before flowing into San Gabriel Reservoir, where it joins the West Fork. West Fork The West Fork, long, originates at Red Box Saddle, a visitor center and frequently used trailhead along the Angeles Crest Highway and about northwest of the summit of Mount Wilson. Beginning at an elevation of , the West Fork flows at a much lower elevation than the East Fork and is the smaller of the two rivers in terms of water volume. The West Fork flows east in a fairly straight course for its entire length. From its headwater the river quickly descends to the Cogswell Reservoir, where Devils Canyon Creek joins from the north. The Gabrielino Trail parallels the river from Red Box Saddle as far as the Devore campground, above Cogswell Reservoir. Below Cogswell Dam the river is paralleled by Forest Route 2N25, a one-lane paved road open only to non-motorized traffic (except for maintenance and emergency services). The river flows east through a twisting canyon, forming the southern boundary of the San Gabriel Wilderness. It receives the tributaries of