Castaic, California is an unincorporated community located in the northern part of Los Angeles County, California. Many thousands of motorists pass through Castaic daily as they drive to or from Los Angeles on Interstate 5. Castaic Lake is part of the California Water Project and is the site of a hydro-electric power plant. Castaic is 41.7 miles northwest of Los Angeles Union Station and due north of the city of Santa Clarita, California.