About Altadena CDP, California
Altadena is a census-designated place (CDP) in Los Angeles County, California, United States. The population was 42,777 at the 2010 census, up from 42,610 at the 2000 census.
Altadena is located at the base of the San Gabriel Mountains. It is bordered on the east by Pasadena and on the north and south by unincorporated areas of Los Angeles County. According to the United States Census Bureau, the CDP has a total area of 8.4 square miles (21.8 km2), over 99% of it land.