Lake San Antonio is a lake located primarily in southern Monterey County, California, and partially in northern San Luis Obispo County, California. The lake is formed by San Antonio Dam on the San Antonio River. The dam is 202 feet tall and was completed in 1965 under Monterey County District Engineer Loran Bunte Jr. The lake and dam are owned by th…Lake San Antonio is a lake located primarily in southern Monterey County, California, and partially in northern San Luis Obispo County, California. The lake is formed by San Antonio Dam on the San Antonio River. The dam is 202 feet tall and was completed in 1965 under Monterey County District Engineer Loran Bunte Jr. The lake and dam are owned by the Monterey County Water Authority. The lake has a capacity of 350,000 acre-feet.