Mount San Antonio, widely known as Mount Baldy or Old Baldy, is the 10,064-foot high point of the San Gabriel Mountains, Los Angeles County, and the greater Los Angeles metropolitan area. Rising on the Los Angeles–San Bernardino county line, it has long been a landmark above the basin and carries older Tongva and Mohave names alongside a Spanish name likely bestowed around 1840. Shaped by compression along the San Andreas Fault system, the mountain has a double summit and drainages that feed both San Antonio Creek and the upper San Gabriel watershed. Its floods, snow, trails, ski hut, and winter hazards have made it both a notable recreation area and a demanding alpine landscape.