San Gabriel Mountains National Monument

The West Fork is one of two major streams, the other being the East Fork, that combine to form the San Gabriel River in Los Angeles County, California. The West Fork flows for 19 miles (31 km) in an easterly direction from its origins at Red Box Gap, in the San Gabriel Mountains, eventually reaching San Gabriel Reservoir where it is bridged by SR 39 just above its mouth. The major tributaries of the West Fork, from upstream to downstream, are Devil Creek, Bear Creek and the North Fork San Gabriel River. A large portion of the watershed is situated in the San Gabriel Wilderness, whose southern boundary is formed by the West Fork. Cogswell Dam impounds the river to create the 10,785-acre-foot (13,303,000 m3) Cogswell Reservoir, whose primary function is flood and silt control for the San Gabriel Valley.The West Fork of the San Gabriel River is a refuge for Southern California wild rainbow trout.

The East Fork is the largest headwater of the San Gabriel River in Los Angeles County, California, United States. It originates at the crest of the San Gabriel Mountains in the Angeles National Forest, at the confluence of the Prairie Fork and Vincent Gulch near Mount Baden-Powell. It then flows south and west for 17 miles (27 km) to San Gabriel Reservoir, where it joins with the West Fork San Gabriel River. Although the East Fork is colloquially considered a separate river (to distinguish it from the West Fork), the U.S. Geological Survey officially lists the East Fork as the upper part of the main stem San Gabriel River, a fact is shown by topographical maps of the area. The major tributaries of the East Fork, from upstream to downstream, are the Prairie Fork, the Fish Fork (which rises near Mount San Antonio/Mount Baldy, the highest summit in the range), the Iron Fork and Cattle Canyon. The "Narrows" of the San Gabriel River is the deepest river gorge in the San Gabriel Mountains, flowing as much as 6,000 feet (1,800 m) below the nearby peak of Iron Mountain. Much of the upper half of the river is within the Sheep Mountain Wilderness. A major point of interest on the East Fork is the Bridge to Nowhere, a 120-foot (37 m) high concrete arch bridge that was once part of the East Fork Road before the rest of the road was destroyed by flooding in 1938. The East Fork Road was originally intended to connect the Los Angeles Basin to the Angeles Crest Highway, but was never completed due to the high cost of cutting and tunneling through the rugged East Fork Canyon. A later attempt to build a road through the East Fork via Shoemaker Canyon, in the 1950s, was also aborted due to lack of funds. Today the East Fork Road provides access to the Heaton Flats trailhead, a popular jumping-off points for visitors to the San Gabriel Mountains. The stretch of the river along and above East Fork Road is one of the most heavily used parts of the Angeles National Forest, and is visited by hikers, campers and recreational gold miners alike – as many as 15,000 per day in the summer, which has had considerable environmental impacts on the East Fork.

The Bobcat Fire was a large wildfire in Los Angeles County and one of the major incidents of the 2020 California wildfire season. The fire ignited on September 6, 2020, and burned 115,997 acres (46,942 ha) before it was fully contained by November 27. The Bobcat Fire primarily burned in the central San Gabriel Mountains, in and around the Angeles National Forest, and is one of the largest fires on record in Los Angeles County to date.

The North Fork San Gabriel River is a tributary, 4.5 miles (7.2 km) long, of the West Fork San Gabriel River in the Angeles National Forest of Los Angeles County, California. The river originates at the confluence of Soldier Creek and Coldbrook Creek in the San Gabriel Mountains below the village of Falling Springs and flows down a steep canyon in a southerly direction to join the West Fork near San Gabriel Reservoir. The North Fork Canyon provides the route for SR 39, one of the main access roads to the Angeles Forest. Crystal Lake, the only natural lake in the San Gabriel Mountains, is located above the headwaters of the North Fork in the Crystal Lake Recreation Area at an elevation of 5,600 feet (1,700 m). The area has campsites, trails and picnic areas and is one of the more popular sites in the Angeles National Forest.

East Fork Road, located in the San Gabriel Mountains above the city of Azusa, California, is a road that gives access from State Route 39 into East Fork and other small townships, including Camp Williams, and Julius Klein Conservation Fire Camp 19, a minor offender prisoner housing complex where "LACO fire personnel provide training, which prepares inmates to safely conduct wild land firefighting operations."The road begins at Route 39, passing over the San Gabriel River, and follows the east fork of the river, crossing a number of small streams. The terminus is Heaton Flats, which has a campsite, a toilet facility, and trails that lead upstream and to the summit of Iron Mountain, 8,007 feet (2,441 m) above. Along East Fork Road there are extensive fire-fighting facilities which are staged to combat the many fires that break out among the foothills above Azusa, Glendora, and San Dimas every year. The road is located within the Angeles National Forest and is managed by the United States Forest Service. The United States Forest Service states that all mining operations, including gold panning, are illegal along the East Fork; however, as mining and prospecting are a historic relic of California's heritage, enforcement of the mining laws is infrequent and gold panning continues along this stretch of the road (which offers easy access to the river). Some of the sites of the area's mining heritage can be accessed from the road by visiting the site of "Eldoradoville", a mining town with three stores and six saloons that was established in 1859 and washed away in the flood of January 18, 1862.East Fork Road was initially planned as an outlet from the Los Angeles Area to State Route 2 and includes a "Bridge to Nowhere" that was abandoned after a flood; a later plan included two never-used tunnels on the aborted Shoemaker Canyon Road.In January 2005 a flood washed out two bridges, which stranded 200 campers and residents for days.

San Gabriel Dam is a rock-fill dam on the San Gabriel River in Los Angeles County, California, within the Angeles National Forest. Completed in 1939, the dam impounds the main stem of the San Gabriel River about 2.5 miles (4.0 km) downstream from the confluence of the river's East and West Forks, which drain a large portion of the San Gabriel Mountains. It is located directly upstream from the Morris Dam. The dam provides flood control, groundwater recharge flows and hydroelectricity for the heavily populated San Gabriel Valley in the Greater Los Angeles metropolitan area.

California 26th congressional district is a congressional district in the U.S. state of California currently represented by Democrat Julia Brownley. The district is located on the South Coast, comprising most of Ventura County as well as a small portion of Los Angeles County. Cities in the district include Camarillo, Oxnard, Santa Paula, Thousand Oaks, Westlake Village, Moorpark, and part of Simi Valley. In 2022, the district lost Ojai and most of Ventura and added Calabasas, Agoura Hills, and the sparsely populated northern half of Ventura County.From 2003 to 2013, the district spanned the foothills of the San Gabriel Valley from La Cañada Flintridge to Rancho Cucamonga. David Dreier, a Republican, represented the district during this period.

Eldoradoville was a gold mining town in Los Angeles County, located in the San Gabriel Mountains. Established in 1859, after gold had been discovered in the river in 1855, Eldoradoville at its peak population had three stores and six saloons. It was washed away on January 18, 1862, in the Great Flood of 1862. One historian described it as "the Downieville of the south—a rough and tough miner's town."The site of Eldoradoville is on the East Fork of the San Gabriel River, on the north side of East Fork Road, where the Eldoradoville Campground is located at an elevation of 1,866 feet (569 m).

Morris Dam (officially the Samuel B. Morris Dam) is a concrete gravity dam across the San Gabriel River in the U.S. state of California. It impounds Morris Reservoir, directly downstream of San Gabriel Dam. The dam was built in the 1930s as a water supply facility for the city of Pasadena, but is now mostly utilized for flood control and flow regulation for groundwater recharge. Situated in northern Los Angeles County, the dam impounds the 417-acre (169 ha) Morris Reservoir in the Angeles National Forest, a few miles northeast of Azusa. From the 1940s to the 1990s, the reservoir was also used for underwater missile testing by the United States military.

Morris Reservoir is located in the San Gabriel Mountains, within the Angeles National Forest, in Los Angeles County, California. It is impounded by Morris Dam, which was completed in 1935. Morris Dam is a gravity dam rising 245 feet (75 m) above the San Gabriel River stream bed.

Big Dalton Dam is a multiple arch concrete dam in Los Angeles County, California, built for the Los Angeles County Flood Control District and completed in August 1929. The dam is one of the earliest of the multiple arch "double-wall" buttress designs of engineer Fred A. Noetzli. The 991 acre-foot (1.2 million cubic meter) dam provides water conservation and controls flooding from Big Dalton Canyon, a watershed within the San Dimas Experimental Forest, part of the Angeles National Forest in the San Gabriel Mountains. It is about 4 miles northeast of the city of Glendora and is operated by the Los Angeles County Department of Public Works.

The San Dimas Biosphere Reserve and Experimental Forest is an experimental forest located in the front range of the San Gabriel Mountains of southern California. San Dimas constitutes a protected field laboratory jointly managed by the Angeles National Forest and the Pacific Southwest Research Station of the United States Forest Service under the designation San Dimas Experimental Forest. It was designated as a UNESCO Biosphere Reserve in 1976 and withdrawn from the programme in July 2018.It encompasses the upper Big Dalton and San Dimas watersheds. The 6,495 hectares (25.08 sq mi) experimental forest was originally established in 1933 and was designated as a biosphere reserve in 1976.San Dimas is a chaparral-dominated Mediterranean ecosystem. In addition to the chaparral vegetation (including chamise), riparian woodland, sage-buckwheat and barren areas, oak woodland and open yellow pine woodlands are represented. The Fern Canyon Research Natural Area is in the remote eastern part the San Dimas reserve. This 555 hectares (2.14 sq mi) Research Natural Area includes Brown's Flat, a locally unique mountain meadow that supports a relict grove of ponderosa pine (Pinus ponderosa Douglas ex C. Lawson).In addition to Fern Canyon, the reserve's research facilities include over 50 gauged watersheds, a lysimeter complex, two major dams and reservoirs—San Dimas Dam and Big Dalton Dam—and three plantations of domestic and introduced trees.Studies at San Dimas have provided valuable information on air pollution, fire effects, erosion, hydrology, and plants and animals in southern California watersheds. The area also provides opportunities for ecological research to many nearby colleges, universities and governmental agencies.Wildfires have frequently burned through the San Dimas area, most recently when the Williams Fire burned much of the forest in September 2002.The forest is currently closed for the general public, except under special written permit. No hunting or other recreational activities are currently allowed.