what county is hillside new jersey
Hillside, New Jersey. Hillside is a township in Union County, New Jersey, United States. As of the 2010 United States Census, the township's population was 21,404, reflecting a decline of 343 (-1.6%) from the 21,747 counted in the 2000 Census, which had in turn increased by 703 (+3.3%) from the 21,044 counted in the 1990 Census.