The East Fork is the largest

headwater The headwaters of a river or stream is the farthest place in that river or stream from its estuary or downstream confluence with another river, as measured along the course of the river. It is also known as a river's source. Definition The ...

of the San Gabriel River in

Los Angeles County Los Angeles County, officially the County of Los Angeles, and sometimes abbreviated as L.A. County, is the most populous county in the United States and in the U.S. state of California, with 9,861,224 residents estimated as of 2022. It is the ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. It originates at the crest of the

San Gabriel Mountains The San Gabriel Mountains ( es, Sierra de San Gabriel) are a mountain range located in northern Los Angeles County, California, Los Angeles County and western San Bernardino County, California, United States. The mountain range is part of the Tr ...

in the

Angeles National Forest The Angeles National Forest (ANF) of the United States Forest Service, U.S. Forest Service is located in the San Gabriel Mountains and Sierra Pelona Mountains, primarily within Los Angeles County, California, Los Angeles County in southern Calif ...

, at the confluence of the Prairie Fork and Vincent Gulch near

Mount Baden-Powell Mount Baden-Powell () is a peak in the San Gabriel Mountains of California named for the founder of the World Scouting Movement, Robert Baden-Powell, 1st Baron Baden-Powell. It was officially recognized by the USGS at a dedication ceremony in ...

. It then flows south and west for to San Gabriel Reservoir, where it joins with the

West Fork San Gabriel River 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 in an easterly direction from its origins at Red Box Gap, in the San ...

. Although the East Fork is colloquially considered a separate river (to distinguish it from the West Fork), the

U.S. Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and ...

officially lists the East Fork as the upper part of the

main stem In hydrology, a mainstem (or trunk) is "the primary downstream segment of a river, as contrasted to its tributaries". Water enters the mainstem from the river's drainage basin, the land area through which the mainstem and its tributaries flow.. A ...

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 San Antonio, commonly referred to as Mount Baldy or Old Baldy, is a summit in the San Gabriel Mountains on the border of Los Angeles and San Bernardino counties of California. Lying within the San Gabriel Mountains National Monument and An ...

/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 below the nearby peak of Iron Mountain. Much of the upper half of the river is within the

Sheep Mountain Wilderness Sheep Mountain Wilderness is a wilderness area of within the San Gabriel Mountains National Monument and managed by the Angeles National Forest. It is within Los Angeles County and San Bernardino County, southern California. The U.S. Congress p ...

. A major point of interest on the East Fork is the

Bridge to Nowhere A bridge to nowhere is a bridge where one or both ends are broken, incomplete, or unconnected to any roads. If it is an overpass or an interchange, the term overpass to nowhere or interchange to nowhere may be used respectively. There are f ...

, a high concrete arch bridge that was once part of the

East Fork Road 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 ...

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 The Angeles Crest Highway is a two-lane (one lane of travel in each direction) highway over the San Gabriel Mountains, in Los Angeles County, California. Its route is to/through the San Gabriel Mountains National Monument and the Angeles Nationa ...

, 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.

References

Rivers of Los Angeles County, California {{California-river-stub

See also

References