City Detials

About the town

Mountainside is a borough in Union County, New Jersey, United States. The borough is located on a ridge in northern-central New Jersey, within the Raritan Valley and Rahway Valley regions in the New York metropolitan area.

Official website


Things to do in town

Resident forum

Important Phone numbers

Borough of Mountainside
Hours of operation 8:30 am – 4:30 pm Monday – Friday