San Bernardino National Forest in the context of San Gorgonio Wilderness

San Gorgonio Mountain, also known locally as Mount San Gorgonio, or Old Greyback, is the highest peak in Southern California and the Transverse Ranges at 11,503 feet (3,506 m).

It is in the San Bernardino Mountains, 27 miles (43 km) east of the city of San Bernardino and 12 miles (19 km) north-northeast of San Gorgonio Pass. It lies within the San Gorgonio Wilderness, part of the Sand to Snow National Monument managed by the San Bernardino National Forest.

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.