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Definition: San Gabriel Mountains from Merriam-Webster's Geographical Dictionary

Mountain range, SW California, SW of Mojave Desert, and NNE of coastal plain in which Los Angeles is situated; chiefly in Los Angeles co.; highest point San Antonio Peak 10,080 ft. (3072 m.).

Summary Article: San Gabriel Mountains
From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide

Mountain range at the junction of the Coast and Transverse ranges in southern California. Located largely within the Angeles National Forest, the range has its highest point at Mount San Antonio or ‘Old Baldy’ (3,105 m/10,080 ft).

The San Gabriel Mountains run east–west for 100 km/63 mi from Cajon Pass at the northwestern end of the San Bernardino Mountains, to Newhall Pass, at the eastern end of the Santa Susana Mountains. Other significant mountains in the range are the twin peaks of North Baldy (2,783 m/9,131 ft) and Mount Baden-Powell (2,865 m/9,399 ft); Mount Wilson (1,740 m/5,710 ft), the site of an important astronomical observatory; and Mount Lukens (1,547 m/5,074 ft), the highest point in the city of Los Angeles. The San Gabriels are much used for recreation, and contain the Sheep Mountain, San Gabriel, and Cucamonga wilderness areas. Their southern foothills are mixed residential and agricultural, and are known especially for the cultivation of citrus fruit.

The action of the San Andreas and numerous other geological faults has resulted in the San Gabriels being among the most fractured ranges in California. Climatically, they form a barrier from dry (northeasterly) desert winds, but also trap the notorious smog of Los Angeles. Notable events in the history of the area include the discovery of gold in Placerita Canyon in 1842, construction of the Mount Lowe Scenic Railway in the 1890s, the creation of California's first forest reserve here in 1892, the opening of the Angeles Crest Highway in 1929, and the damming of the Big Tujunga Canyon (the ‘Big T’) to control run-off into the San Fernando Valley. Up to 1927, the San Gabriels were sometime referred to as the ‘Sierra Madre’.

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