Town guide · Union County
Living in Mountainside, NJ
Mountainside is a small residential borough on a ridge in Union County, home to much of the Watchung Reservation and to Echo Lake Park. Route 22 runs through the middle of town, but zoning limits commercial development along the highway, so most of the borough is homes and parkland.
- County
- Union
- Population
- About 7,000 (2020 census)
- Size
- About 4 square miles
- Setting
- Residential borough on a ridge, bordered by county parkland
- Main roads
- U.S. Route 22, with Interstate 78 along the border with Summit
The borough
Homes between two county parks
Mountainside became a borough in 1895, formed from part of Westfield Township. It is bordered by Summit to the north, Springfield to the east, Westfield to the south and Berkeley Heights and Scotch Plains to the west, and it uses a single ZIP code, 07092.
Two large Union County parks, the Watchung Reservation and Echo Lake Park, are in the borough. In 1958 the Army built part of a Nike missile battery here, with its launchers in Mountainside and its radar in Berkeley Heights. It closed in 1963, and the cleared land in the reservation became the Watchung Stables.
Homes
What you will find
- Single family homes: Mountainside is mostly single family homes, about 2,600 homes in all.
- Limited commercial land: Unlike most towns along Route 22, Mountainside's zoning does not allow much commercial development along the highway.
Worth knowing: Mountainside is small and mostly residential, so close comparisons are few and each street can price differently. Lots on the ridge vary a great deal, and we check the FEMA flood map on every address before pricing a home or writing an offer.
Property taxes
What taxes look like in Mountainside
- 1.566%2025 effective tax rate, as a share of market value
- $13,3092025 average residential tax bill
A home worth $850,000 on today's market would pay roughly $13,311 a year at Mountainside's 2025 effective rate. Your actual bill depends on your assessment, so we pull the real tax record for any home you are considering.
Source: New Jersey Division of Taxation, 2025 general and effective tax rates. Rates are set each year.
Getting around
Roads and commuting
U.S. Route 22 runs through the middle of Mountainside, and for about a mile the eastbound shoulder can be used by buses at peak hours. Interstate 78 briefly forms the border between Mountainside and Summit, and its interchanges are in neighboring towns. There is no train station in the borough. Summit station, about two miles from the center of town, has frequent direct trains to New York Penn Station, and Westfield station on the Raritan Valley Line is about four miles away. NJ Transit buses 114 and 117 run to the Port Authority Bus Terminal in New York, and routes 65 and 66 run to downtown Newark. Newark Liberty International Airport is about 11 miles east.
Places worth knowing
Parks, landmarks and open space
- Watchung Reservation: Union County's preserve of about 2,000 acres of woods, fields, lakes and streams, with more than 13 miles of hiking trails, Lake Surprise and the Watchung Stables.
- Trailside Nature and Science Center: The county's environmental education center on New Providence Road inside the reservation, with hands on exhibits and a planetarium.
- Echo Lake Park: A 139 acre Union County park with two lakes, fishing, ball fields, a dog run and a county September 11 memorial.
- Hetfield House and Levi Cory House: Two historic houses moved to Constitution Plaza, the Hetfield House built around 1763 and the Levi Cory House built around 1818.
Common questions
Questions people ask us about Mountainside
What are property taxes in Mountainside, NJ?
Mountainside Borough's 2025 effective tax rate is 1.566 percent of market value, and the average residential tax bill is $13,309, according to the New Jersey Division of Taxation. Actual bills depend on each home's assessment.
Is the Watchung Reservation in Mountainside?
Much of it is. The Union County preserve of about 2,000 acres has its Trailside Nature and Science Center at 452 New Providence Road in Mountainside. Parts of the reservation extend into neighboring towns, including the Deserted Village of Feltville on the Berkeley Heights side.
Is there a train station in Mountainside?
No. Summit station, about two miles from the center of town, offers direct trains to New York Penn Station, and Westfield station is about four miles away. NJ Transit buses 114 and 117 run from Mountainside to the Port Authority Bus Terminal.
Was there really a missile site in Mountainside?
Yes. In 1958 part of a Nike missile battery was installed, with its launchers in Mountainside and its radar station in Berkeley Heights. It operated until 1963, and the cleared area of the Watchung Reservation became the Watchung Stables.
Nearby towns
Towns that border Mountainside
Buying or selling in Mountainside?
Few homes, careful pricing
With only about 2,600 homes in Mountainside, good comparisons are scarce, so we study your lot and street with care. Then we give you our straight read on value and on each way to sell.
Call or text either of us directly.