High Quality Content by WIKIPEDIA articles! Hawthorne (pronounced HAW-thorn) is a borough in Passaic County, New Jersey, United States. As of the 2010 United States Census, the borough population was 18,791 reflecting an increase of 573 (+3.1%) from the 18,218 counted in the 2000 Census, which had in turn increased by 1,134 (+6.6%) from the 17,084 counted in the 1990 Census.