The San Bernardino area is a semiarid inland valley of about 120 square miles in southwestern San Bernardino County, about 60 miles east of Los Angeles, in the upper part of the Santa Ana River drainage basin. The San Bernardino area was defined by Dutcher and Garrett (1963) as a northwest-trending area between the San Andreas and San Jacinto faults. The area is bordered on the northwest by the San Gabriel Mountains, on the northeast by the San Bernardino Mountains, on the south by the badlands and Crafton Hills, and on the southwest by a low, east-facing escarpment of the San Jacinto fault. Alluvial fans extend from the base of the mountains and hills that surround the valley and coalesce to form a broad, sloping alluvial plain in the central part of the valley. Altitude ranges from about 1,000 feet (ft) near the city of San Bernardino to more than 10,000 ft in the San Bernardino Mountains.