Mountainside, New Jersey

Mountainside, New Jersey
Trailside Nature & Science Center in Watchung Reservation in Mountainside
Map of Mountainside in Union County. Inset: Union County highlighted in the State of New Jersey.
Census Bureau map of Mountainside, New Jersey
Mountainside
Location in Union County
Mountainside
Location in New Jersey
Mountainside
Location in the United States
Coordinates: 40°40′51″N 74°21′37″W / 40.680722°N 74.360292°W / 40.680722; -74.360292
Country United States
State New Jersey
CountyUnion
IncorporatedSeptember 25, 1895
Government
  TypeFaulkner Act (mayor–council)
  BodyBorough Council
  MayorPaul N. Mirabelli (R, term ends December 31, 2027)
  AdministratorGlenn Mortimer
  Municipal clerkMartha Lopez
Area
  Total
4.04 sq mi (10.47 km2)
  Land4.00 sq mi (10.35 km2)
  Water0.04 sq mi (0.12 km2)  1.11%
  Rank295th of 565 in state
12th of 21 in county
Elevation
233 ft (71 m)
Population
 (2020)
  Total
7,020
  Estimate 
(2023)
6,924
  Rank319th of 565 in state
19th of 21 in county
  Density1,756.8/sq mi (678.3/km2)
   Rank312th of 565 in state
21st of 21 in county
Time zoneUTC−05:00 (Eastern (EST))
  Summer (DST)UTC−04:00 (Eastern (EDT))
ZIP Code
07092
Area code908
FIPS code3403948510
GNIS feature ID0885311
Websitewww.mountainside-nj.com

Mountainside is a borough in Union County, in the U.S. state of New Jersey. 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. As of the 2020 United States census, the borough's population was 7,020, an increase of 335 (+5.0%) from the 2010 census count of 6,685, which in turn reflected an increase of 83 (+1.3%) from the 6,602 counted in the 2000 census.

Mountainside was incorporated as a borough on September 25, 1895, from portions of Westfield Township, based on the results of a referendum held the previous day.

New Jersey Monthly magazine ranked Mountainside as its 16th best place to live in its 2008 rankings of the "Best Places To Live" in New Jersey, as well as eighth in the 2010 list.