The San Bernardino National Forest is a United States National Forest in Southern California encompassing 823,816 acres (3,333.87 km2) of which 677,982 acres (2,743.70 km2) are federal. The forest is made up of two main divisions, the eastern portion of the San Gabriel Mountains and the San Bernardino Mountains on the easternmost of the Transverse Ranges, and the San Jacinto and Santa Rosa Mountains on the northernmost of the Peninsular Ranges. Elevations range from 2,000 to 11,499 feet. The forest includes seven wilderness areas: San Gorgonio, Cucamonga, San Jacinto, South Fork, Santa Rosa, Cahuilla Mountain and Bighorn Mountain. Forest headquarters are located in the city of San Bernardino. There are district offices in Lytle Creek, Idyllwild, and Fawnskin.

The San Gabriel Mountains comprise a mountain range located in northern Los Angeles County and western San Bernardino County, 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.