Mountainside is a borough in Union County, New Jersey, United States. As of the 2010 United States Census, the boroughs population was 6,685, reflecting an increase of 83 (+1.3%) from the 6,602 counted in the 2000 Census, which had in turn declined by 55 (0.8%) from the 6,657 counted in the 1990 C
Download Image: download
