Castro Valley is the largest unincorporated area in Alameda County and one of the largest unincorporated areas in the country. Castro Valley is 16 square miles of quiet, well-defined neighborhoods full of charming homes making it a friendly, great place to raise a family. Castro Valley has a highly regarded school system as well as a new Performing Arts Center and a new Sports Stadium. Its local shopping areas helps it retain its small town feel while being situated less than 30 miles from San Francisco. An average temperature of 65° makes it a highly desirable area in Northern California to live.