Much of 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-Cucamonga Fault Zones to the south. This tectonic block was uplifted during the
Miocene and has since been
dissected by numerous rivers and washes.
Setting and elevation The highest elevation, Mount San Antonio (Mount Baldy) at , 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, the San Gabriel Mountains crest abruptly up to about .
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, is Mount Gleason, which at , is the highest in this region of the San Gabriels. South of the gorge is the southern "foothills" of the mountains, which rise abruptly 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 . On 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 in length that includes most of the highest peaks in the range:
Waterman Mountain, at ;
Mount Islip, at ,
Mount Baden-Powell, at ,
Pine Mountain, at , and
Mount San Antonio, the highest peak in the range at . 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 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. canyon, looking west East of San Antonio Canyon, 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 ,
Cucamonga Peak, at , and
Ontario Peak, rising .
Lytle Creek, flowing generally southeast, drains most of 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.
Locale 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,
Rialto and
West San Bernardino. The north side of 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.
Hydrology Melting snow and rain runoff on 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 eastward, and the East Fork, starting north of Mount San Antonio, flows south and west through 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, draining the mountains near
Azusa, flowing into the urban
San Gabriel Valley, and eventually to the
Pacific Ocean near
Seal Beach.
Peaks , from Devils Backbone San Gabriel Mountains peaks within the Angeles National Forest include: •
Mount San Antonio (Mount Baldy), •
Pine Mountain, • Dawson Peak, •
Mount Harwood, •
Mount Baden-Powell, •
Throop Peak, •
Mount Burnham, •
Telegraph Peak, •
Cucamonga Peak, •
Ontario Peak, • Mount Lewis, •
Timber Mountain, •
Mount Islip, — site of historic Mt. Islip fire lookout tower • Mount Williamson, •
Waterman Mountain, •
Iron Mountain, •
South Mount Hawkins, — lookout destroyed in Curve Fire, 2002 •
Pallett Mountain, •
Pacifico Mountain, •
Mount Gleason, •
Strawberry Peak, •
San Gabriel Peak, •
Mount Disappointment, •
Mount Lawlor, •
Vetter Mountain, — site of historic Vetter Mountain
Fire lookout tower • Rattlesnake Peak, •
Mount Wilson, — location of the
Mount Wilson Observatory •
Mount Lowe, — site of
Mount Lowe Railway • Iron Mountain, •
Josephine Peak, •
Condor Peak, •
Monrovia Peak, • Rankin Peak, •
Smith Mountain, •
Mount Lukens, • Mount McKinley, •
Magic Mountain, • Mendenhall Peak, • Clamshell Peak, • Los Piñetos Peak • Kagel Mountain, •
Potato Mountain, •
Echo Mountain, • Bare Mountain 6,388 ft (1,947 m) •
Hoyt Mountain 4,416 ft (1,346 m) ==Climate==