Mountainside borough, New Jersey
Official LSAD Designation: Mountainside borough • Census GEOID: 3448510
• Union County
Mountainside borough is an incorporated borough in Union County, New Jersey. According to official records from the Census (2025), Mountainside borough had an estimated population of 7,346 residents. Official Census Bureau geographic records classify this community under LSAD designation Mountainside borough (GEOID 3448510).
Local Government Administration U.S. Census Bureau GMAF
Borough Of Mountainside
Municipal
Official Title:
Municipal Clerk
Address:
1385 US HIGHWAY 22, 1, MOUNTAINSIDE NJ 07092-2697
County Of Union
County
Official Title:
Clerk Of The Board
Address:
10 ELIZABETHTOWN PLZ, ELIZABETH NJ 07207-3451
Civic & Statistical Snapshot
| Category | Estimate | Survey Period / Source |
|---|---|---|
| Total Population | 7,346 | 2025 |
| Median Household Income | $211,538 | 2020-2024 |
| Median Home Value | $810,300 | 2020-2024 |
| Land Area | 4.00 sq mi | Gazetteer (2026) |
| Civic & Public Services | Hospitals, Libraries, Colleges | CMS / IMLS / IPEDS |
| Schools & Districts | NCES Directory Listings | Provided by k12guides.com |
| Nearby Airports | Landing Facilities | Provided by airport-data.com |
| Climate & Weather | NOAA 30-Year Normals | 1991–2020 |
Source: U.S. Census Bureau (PEP, ACS 5-Year).