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48-492: The dam is 124 ft (38 m) high from foundation to crest and spans 576 ft (176 m) across the canyon, forming a reservoir with a capacity of 3,700 acre⋅ft (4,600,000 m). The reservoir has a surface area of 108 acres (44 ha) and receives water from a drainage area of 63.7 sq mi (165 km) on the north slope of the San Gabriel Mountains . A formerly popular recreation spot,

96-511: A $ 45 million project to reconstruct the roadway, construct soldier pile retaining walls, repair drainage systems, install rockfall protection, and provide asphalt concrete overlay and traffic striping, should begin in fall 2010." In 2011, the planned repair of the road was abruptly terminated, due to concern of high future maintenance costs, and potential impact on the local bighorn sheep population. However, in October 2016, Caltrans announced it

144-502: A hiker gets lost or stuck on a mountain ledge or may fall downhill. Some of the more extreme cases of emergency search-and-rescue efforts will often be given air time on Los Angeles television and radio newscasts. The Pacific Crest Trail passes along the mountain ridge. During the winter, many Southern California mountaineers climb a variety of snow routes and even some ice routes in the San Gabriel Mountains. Baldy Bowl

192-657: A nearly two-hour trip. Reopening Highway 39 would cut the drive-time to the Waterman Ski Area in half and shorten the trip east to Wrightwood. According to the Caltrans District Seven "Inside Seven" Newsletter, "Two projects that will address those issues and get the highway reopened are scheduled for construction soon. The first, building two retaining walls near the city of Azusa from Old San Gabriel Canyon Road to approximately 4 miles (6.4 km) south of SR-2, could begin in mid-2009. The second,

240-504: A safe eating advisory for Little Rock Reservoir based on levels of mercury or PCBs found in fish caught from this water body. San Gabriel Mountains The San Gabriel Mountains ( Spanish : Sierra de San Gabriel ) comprise a mountain range located in northern Los Angeles County and western San Bernardino County, California , United States. The mountain range is part of the Transverse Ranges and lies between

288-627: A steep, rugged and precipitous gorge. The two meet at San Gabriel Reservoir , and turn south, boring through the southern portion of the San Gabriels, emptying of the mountains near Azusa into the urban San Gabriel Valley , and eventually to the Pacific Ocean near Seal Beach . San Gabriel Mountains peaks within the Angeles National Forest include: The climate of the range varies with elevation from continental to

336-696: A way to counter the shortage of parks and open space in Los Angeles County which they claim has contributed to high childhood obesity rates. The Obama administration cited the presence of endangered species, important cultural resources, and the threat of unreliable funding for management and encroaching development as the proximal reasons for the establishment of the monument. In addition, all existing rights-of-way continue to be honored and existing recreational activities — such as hiking, camping, fishing and cycling — will be unaffected. Local officials, including Los Angeles Mayor Eric Garcetti , cheered

384-709: Is Mount Gleason, which at 6,502 feet (1,982 m), is the highest in this region of the San Gabriels. South of the gorge is the southern "foothills" of the mountains, which rise abruptly 4,000 feet (1,200 m) above the Los Angeles Basin and give rise to the Arroyo Seco , a tributary of the Los Angeles River . Southeast of Big Tujunga Canyon, the southern front range of the San Gabriels gradually grows in elevation, culminating in notable peaks such as Mount Wilson at 5,710 feet (1,740 m). On

432-715: Is a United States National Monument managed by the U.S. Forest Service , which encompasses parts of the Angeles National Forest and the San Bernardino National Forest in California. On October 10, 2014, President Barack Obama used his authority under the Antiquities Act to create the new monument, protecting 346,177 acres of public lands in the San Gabriel Mountains of the Transverse Ranges . The effort to protect

480-542: Is by far the most popular route, getting hundreds of climbers per season. There are many other routes, offering a variety of choices. Rock climbing is not as common in the San Gabriel Range as it is in neighboring areas, as this range is famous for loose rock. Various faults crisscross the range, making it one of the steepest and fastest-growing ranges in the world. Plate tectonic activity breaks up most rock, making it unsuitable for rock climbing. Williamson Rock

528-598: Is low. The design changes resulted in the dam being taken off the NRHP. The dam was also raised 12 ft (3.7 m) and a new spillway added, increasing the reservoir capacity to its current 3,700 acre⋅ft (4,600,000 m). The dam and reservoir are scheduled for a major renovation project in three separate phases. The first phase begins with construction of a subterranean grade control structure within Littlerock Reservoir at Rocky Point. The second phase

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576-622: Is much better, and it is open much of the winter. State Route 39 connected the city of Azusa with the Angeles Crest Highway until it was seriously damaged by landslides, first in 1978, and again in 2005. The highway was opened to emergency crews in February 2003. People heading to Mount Waterman must now travel west to Pasadena and then travel on the Angeles Crest Highway (Highway 2) in La Cañada Flintridge,

624-430: Is the removal of 1,165,000 cubic yards (891,000 m) of accumulated sediment from within the reservoir over a seven- to twelve-year time frame. Finally, scheduled ongoing sediment removal of approximately 38,000 cubic yards (29,000 m) per year to maintain design capacity. There are no plans to reopen its facilities to the public. The California Office of Environmental Health Hazard Assessment (OEHHA) has developed

672-584: The Los Angeles Basin and the Mojave Desert , with Interstate 5 to the west and Interstate 15 to the east. The range lies in, and is surrounded by, the Angeles and San Bernardino National Forests, with the San Andreas Fault as its northern border. The highest peak in the range is Mount San Antonio , commonly referred to as Mt. Baldy. Mount Wilson is another notable peak, known for

720-854: The Miocene and has since been dissected by numerous rivers and washes. The highest elevation, Mount San Antonio (Mount Baldy) at 10,069 feet (3,069 m), rises towards the eastern extremity of the range which extends from the Cajon Pass (Interstate 15) on the east, where the San Gabriel Mountain Range meets the San Bernardino Mountain Range , westward to meet the Santa Susana Mountains at Newhall Pass (Interstate 5). South and east of Santa Clarita and north of San Fernando ,

768-608: The Mount Wilson Observatory and the antenna farm that houses many of the transmitters for local media. The observatory may be visited by the public. On October 10, 2014, Barack Obama designated the area the San Gabriel Mountains National Monument . The Trust for Public Land has protected more than 3,800 acres (1,500 ha) of land in the San Gabriel Mountains, its foothills, and the Angeles National Forest. Much of

816-651: The Victor Valley and the western Cajon Valley. Past its junction with Angeles Forest Highway, traveling east, Angeles Crest Highway features blind curves, various bumps, and potholes. This section of the "Crest" is closed during the winter due to rockfall and avalanche hazards. State Route 2, just past Mountain High , is called the Big Pines Highway to the Route 138 junction. Another key county route through,

864-476: The 1970s, it was listed on the National Register of Historic Places (NRHP). In 1994, the last major renovation of the dam was completed, which involved strengthening the face with roller-compacted concrete , hiding the original multiple-arch design and transforming it to resemble a conventional gravity dam. The arches are still visible on the back face of the dam when the water level in the reservoir

912-665: The Mediterranean, with mostly dry summers (except for scattered summer thunderstorms) and cold, wet winters. Snow can fall above 4,000 ft (1,200 m) elevation during frontal passages between November and April, but is most common in December through March. Annual precipitation totals are mostly in excess of 25 in (640 mm) on the coastal (southern) slopes above 3,000 ft (900 m) elevation, with up to 45 in (1,100 mm) falling in some areas above 5,000 ft (1,500 m). The coastal (south) side of

960-616: The North American west coast. Like nearly all of the other mountains in the Transverse Ranges , the San Gabriels are a series of fault blocks that were uplifted in the Cenozoic . Tectonic uplift rates and erosion rates systematically increase as topography steepens eastward in the San Gabriel Mountains, where the San Andreas and San Jacinto faults meet. Current rates of erosion in the eastern San Gabriel mountains are among

1008-622: The San Andreas Fault produces numerous springs, sag ponds, and wetland areas that are critical habitats for a variety of native species. Larger animals include California mule deer , California black bear , San Pedro Martir coyote and the rarely seen mountain lion or cougar. Smaller mammals include raccoons, opossum, skunk, and bobcats. Golden and bald eagles are found rarely, but hawks are common. Rattlesnakes are common and often encountered on trails by hikers. Critically endangered yellow-legged frogs have declined or vanished from

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1056-679: The San Gabriel Mountains began more than a century earlier, in 1891 with another U.S. President, Benjamin Harrison , the 23rd president, using a congressional act, to designate and delineate the first federal protection in the United States of forested lands, using the same mountain range name, as the San Gabriel Timberland Reserve . Two earlier California conservationists, Abbot Kinney and John Muir , influenced President Benjamin Harrison . The monument covers

1104-648: The San Gabriel Mountains crest abruptly up to about 4,000 feet (1,200 m). Pacoima and Big Tujunga Canyons cut through the range just east of San Fernando, carrying runoff into the San Fernando Valley . Little Tujunga Canyon Road bridges the range in this area, connecting the San Fernando Valley to the Santa Clara River valley in the north. Towering over Big Tujunga Canyon north of Big Tujunga Reservoir , and south of Acton,

1152-669: The central and northern regions of the San Gabriel Mountains, extending west to east from Upper Sand Canyon at Little Tujunga Canyon Road to Telegraph Peak . It contains the Sheep Mountain Wilderness , the San Gabriel Wilderness , and Pleasant View Ridge Wilderness. Most of the major peaks of the San Gabriels are within the limits of the monument, including Mount San Antonio , Mount Baden-Powell , and Throop Peak . The Silver Moccasin Trail lies within

1200-567: The dam, reservoir, and vicinity used to receive about 300,000 visitors each year, but since 2015, the facilities have been closed to the public. Designed by John S. Eastwood , a noted engineer of several dams in the western U.S., Littlerock was built in 1924 by the Palmdale Irrigation District (now Palmdale Water District) to provide a water supply for orchards in the area. With a height of 112 ft (34 m) and holding 2,400 acre⋅ft (3,000,000 m) of water, it

1248-976: The extreme eastern San Gabriels. The range terminates at Cajon Pass, through which runs Interstate 15 , and beyond which rise the even higher San Bernardino Mountains . The Range is bounded on the north by the Antelope Valley and the Mojave Desert and to the south by the communities of Greater Los Angeles . The south side of the range is almost continuously urbanized and includes the Los Angeles city communities of Sylmar , Pacoima , and Sunland-Tujunga , as well as cities and unincorporated areas of San Fernando , La Crescenta , La Cañada Flintridge , Altadena , Pasadena , Sierra Madre , Arcadia , Monrovia , Bradbury , Duarte , Azusa , Glendora , San Dimas , La Verne , Claremont , Upland , Rancho Cucamonga , Fontana , and Rialto . The north side of

1296-527: The fastest in the continental United States and have accelerated in response to the increased frequency of wildfires over the 1900s. Over future centuries, it remains unclear whether soil and brush ecosystems in the San Gabriel mountains will continue to re-establish soil and vegetation after increasing fire and soil-erosion frequencies, or if increasing fire frequencies and erosion will strip soils and permanently alter soil cover and vegetation types across

1344-430: The highest peak in the range at 10,068 feet (3,069 m). On the north slopes of the San Gabriel crest, the northern ranks of mountains drop down incrementally to the floor of the Mojave Desert in a much more gradual manner than the sheer southern flank. The Angeles Crest Highway , one of the main routes across the San Gabriels, runs through this area from west to east. Little Rock, Big Rock, and Sheep Creeks drain off

1392-471: The monument was in response to decades of input and support from the local community demanding greater environmental protections for the heavily touristed region. There have been longstanding concerns about pollution and vandalism in the region's subalpine forests and watersheds. Public health and Latino groups also advocated for protecting the public lands in the San Gabriel Mountains as an opportunity to protect access to open space and outdoor recreation as

1440-553: The monument. The monument only covers a limited portion of the range's western extent, and much of the southern portion of the range has been excluded from the monument. It does not contain the Cucamonga Peak region. The movement to further preserve the San Gabriel Mountains began in 2003 when then Congresswoman Hilda Solis initiated an environmental feasibility report to see if it was possible to increase protection by National Monument designation. The National Monument

1488-495: The mountain ecosystem. There are both areas of conifer as well as broadleaf forestation, including the presence of some endemic taxa. Conifer (pine, fir, cedar) and oak forests are most widespread above 5,000 feet (1,500 m) where the precipitation is above 30 inches (760 mm) (the central and eastern high San Gabriels). In the wetter areas, madrone and bay laurel trees also occur in places, and ferns are common. Trees like willow, alder, and cottonwood are also found throughout

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1536-566: The mountains during big storms often produces flooding in adjacent foothill communities (especially in areas denuded by wildfires). The range is mostly smog-free above 5,000 ft (1,500 m) elevation, above the inversion layer. The large telescope installation at Mt. Wilson is a testimony to the clear atmospheric conditions that prevail, although light pollution from the L.A. basin below has hindered telescope activities in recent decades. The San Gabriel Mountains see wildfires frequently. The fires are often driven by dry Santa Ana wind events in

1584-425: The mountains is Angeles Forest Highway . Angeles Forest Highway begins 11 miles northeast of La Cañada Flintridge at its Angeles Crest Highway junction. Ending near Acton , it allows easy access to the central Forest and the fast-growing Antelope Valley . Because the "Forest" and the 11-mile (18 km) "Crest" portion leading to La Cañada Flintridge is well-traveled by Antelope Valley commuters, its road maintenance

1632-409: The news along with Hispanic, recreation, and conservation groups. Its establishment faced limited opposition from local residents. To alleviate concerns, the extent of the monument does not cover most of the southern slopes of the San Gabriel Mountains, and excludes towns in the region. In May of 2023, Representative Judy Chu and Senator Alex Padilla introduced a package of bills that would expand

1680-596: The north the range is abruptly dissected by the canyon of the West Fork San Gabriel River. Even further north the range slopes up into the towering main crest of the San Gabriels, a sweeping arc-shaped massif 30 miles (48 km) in length that includes most of the highest peaks in the range: Waterman Mountain , at 8,038 feet (2,450 m); Mount Islip , at 8,250 feet (2,510 m), Mount Baden-Powell , at 9,399 feet (2,865 m), Pine Mountain , at 9,648 feet (2,941 m), and Mount San Antonio ,

1728-455: The northern part of the mountains, forming large alluvial fans as they descend into the Mojave. To the east, the San Andreas Fault cuts across the range, forming a series of long, straight, and narrow depressions, including Swarthout Valley and Lone Pine Canyon. South of Mount San Antonio, San Antonio Creek drains the mountains, cutting the deep San Antonio Canyon. East of San Antonio Canyon,

1776-493: The range along with the stream courses (riparian habitat), even at lower elevations. Chaparral (dense shrub, brush, and small tree) vegetation is widespread where there is no continuous tall tree cover, especially at lower elevations. Chaparral is highly adapted to fire and replaces trees for decades after fires. There is a subspecies of the Leather Oak which is found only within the San Gabriel Mountains. The Rift Zone along

1824-614: The range features rolling peaks. The range lacks craggy features, but contains a large number of canyons and is generally very rugged and difficult to traverse. The San Gabriel Mountains are composed of a large fault block between the San Andreas Fault Zone to the north, and the San Gabriel Fault and the Sierra Madre and Cucamonga Fault Zones to the south. This tectonic block was uplifted during

1872-482: The range gradually loses elevation, and the highest peaks in this section of the mountain range are in the south, rising dramatically above the cities of Claremont , Upland and Rancho Cucamonga . However, there are still several notable peaks in this region, including Telegraph Peak , at 8,985 feet (2,739 m), Cucamonga Peak , at 8,859 feet (2,700 m), and Ontario Peak , rising 8,693 feet (2,650 m). Lytle Creek , flowing generally southeast, drains most of

1920-437: The range is less densely populated and includes the city of Palmdale as well as the small unincorporated towns of Acton , Littlerock , Pearblossom , Valyermo , Llano , Piñon Hills , and Phelan . At the west end of the range lies the city of Santa Clarita . Within the mountains themselves are the small unincorporated communities of Mount Baldy , Wrightwood , Big Pines and Lytle Creek . Melting snow and rain runoff on

1968-417: The range receives more precipitation than the desert (northern) side. The highest precipitation is found in the central and eastern parts of the range (Mt. Wilson to Mt. San Antonio). Annual precipitation totals are highly variable from year to year, and can be extremely high during wet El Nino years (sometimes over 70 in (1,800 mm), with single storm totals over 10 in (250 mm)). Runoff from

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2016-564: The south side of the San Gabriels' highest mountains give rise to its largest river, the San Gabriel River . Just to the west of Mount Hawkins , a north-south divide separates water running down the two main forks of the river and their tributaries. The West Fork, beginning at Red Box Saddle, runs 14 miles (23 km) eastward, and the East Fork, starting north of Mount San Antonio, flows 18 miles (29 km) south and west through

2064-477: The streams due to the loss of suitable habitat. The introduction of invasive predators like trout, which feed on tadpoles, decimated their population. The main road that runs through the San Gabriel Mountains is the Angeles Crest Highway , State Route 2 . It starts in the southwest at the city of La Cañada Flintridge and ends at its junction with State Route 138 , just past Wrightwood , near

2112-544: The summer and fall. Notable wildfires in the San Gabriel Mountains have included the 2009 Station Fire , 2020 Bobcat Fire , and the 2024 Bridge Fire . Granitic and metasedimentary rocks are the primary constituent of the San Gabriel Mountains. Metasedimentary rocks were attached to the North American craton in the Precambrian eon, and granitic rocks formed throughout the Mesozoic as oceanic plates subducted underneath

2160-453: Was again considering plans to re-open the road, after pressure from local communities. In the winter, snowboarding and skiing are quite popular in the San Gabriels, at Mountain High and Mt. Baldy . The two other resorts, Mount Waterman and Kratka Ridge , are rarely open due to insufficient snow. In the summer, canyoneering , hiking, backpacking, picnicking, and camping are some of the activities popular with visitors. From time to time,

2208-451: Was established on October 10, 2014, by proclamation of President Barack Obama under the Antiquities Act . More than 15 million people live within 90 minutes of the San Gabriel Mountains, which provides 70 percent of the open space for Angeleños and 30 percent of their drinking water . Polling indicated that 80 percent of Los Angeles County voters supported the proposed protection of the San Gabriel Mountains and rivers. The creation of

2256-531: Was the most famous climbing area until it was closed for climbing. There are many other craggy areas scattered about the range that provide mostly traditional climbing opportunities. Angeles National Forest Fire Lookout Association has rebuilt and operates Vetter Mountain Lookout , and Slide Mountain Lookout . The organization is rebuilding South Mount Hawkins Lookout . San Gabriel Mountains National Monument The San Gabriel Mountains National Monument

2304-503: Was the tallest multiple-arch reinforced concrete dam in the world at the time. The dam's design combined with its record height was highly controversial; the state mandated renovations in 1932, in which concrete buttresses were added to the dam face. In 1938, the dam nearly failed as a result of historic flooding , which led to the evacuation of hundreds of people in downstream towns. The dam was renovated again in 1966 to comply with increasing safety standards and regional urban development. In

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