On October 10, 2014, President Barack Obama designated the area the San Gabriel Mountains National Monument.

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 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.

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.

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 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.

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 a steep, rugged and precipitous gorge.

Runoff from the mountains during big storms often produces flooding in adjacent foothill communities (especially in areas denuded by wildfires).

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.

[12][13] Current rates of erosion in the eastern San Gabriel mountains are among the fastest in the continental United States[14] and have accelerated in response to the increased frequency of wildfires over the 1900s.

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).

Trees like willow, alder, and cottonwood are also found throughout the range along with the stream courses (riparian habitat), even at lower elevations.

[17] The Rift Zone along the San Andreas Fault produces numerous springs, sag ponds, and wetland areas that are critical habitats for a variety of native species.

[18] The main road that runs through the San Gabriel Mountains is the Angeles Crest Highway, State Route 2.

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 is much better, and it is open much of the winter.

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, 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.

[citation needed] The two other resorts, Mount Waterman and Kratka Ridge, are rarely open due to insufficient snow.

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.