Angeles National Forest in the context of "Big Pines, California"

Mount Wilson is at the peak of the San Gabriel Mountains, located within the San Gabriel Mountains National Monument and Angeles National Forest in Los Angeles County, California. With only minor topographical prominence the peak is not naturally noticeable from a distance, although it is easily identifiable due to the large number of antennas near its summit. It is a subsidiary peak of nearby San Gabriel Peak. Quartz diorite is the dominant bedrock.

It is the location of the Mount Wilson Observatory, which is an important astronomical facility in Southern California with historic 60-inch (1,524 mm) and 100-inch (2,540 mm) aperture telescopes, and 60-foot (18.3 m) and 150-foot (45.7 m) tall solar towers. The newer CHARA Array, run by Georgia State University, is also sited there and does important interferometric stellar research.

The San Gabriel Mountains (Spanish: Sierra de San Gabriel) are a mountain range located in Los Angeles and San Bernardino counties, California, United States. The mountain range is part of the Transverse Ranges and lies between 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 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, President 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. The mountains were once known as the Sierra Madre, lending the name to the city of Sierra Madre; however, since 1965, the name "Sierra Madre" has referred to a different mountain range to the west in Santa Barbara County.