Altadena is an unincorporated census-designated place of Los Angeles County in the state of California, in the United States. 42,610 people were living in Altadena as of 2000. It is about fourteen miles from downtown Los Angeles. It was built as a suburb of Pasadena in 1887. However, although it was meant to be a suburb of Pasadena, it has so far refused to become part of Pasadena.