Mountainside Flag

Mountainside

County:
Union County
County Seat:
No
Area (mi²):
3.996
State:
New Jersey

Mountainside is a borough located in Union County, New Jersey. Mountainside has a 2025 population of 6,881. Mountainside is currently declining at a rate of -0.3% annually and its population has decreased by -1.53% since the most recent census, which recorded a population of 6,988 in 2020.

The average household income in Mountainside is $235,424 with a poverty rate of 2.85%. The median age in Mountainside is 48.7 years: 49.7 years for males, and 45.3 years for females.

6.9K
Total Population
1,722
Density (mi²)
-21 -0.3%
Growth

Mountainside Population

Mountainside Population

Data after 2023 is projected based on recent change

Demographics

The racial composition of Mountainside includes 75.28% White, 12.33% Asian, and smaller percentages for Black or African American, other race and multiracial populations.

Population by Race

White (75.3%)

Asian (12.3%)

Two or more races (11.2%)

Black or African American (1.1%)

Other race (0.0%)

Race
Population
Percentage (of total)
White5,24575.28%
Asian85912.33%
Two or more races78311.24%
Black or African American771.11%
Other race30.04%

Mountainside Marital Status

OverallMalesFemales0%10%20%30%40%50%60%70%80%90%100%

Married

Widowed

Divorced

Separated

Never Married

Economics and Income Statistics

Mountainside's average per capita income is $104,750. Household income levels show a median of $210,100. The poverty rate stands at 2.85%.

Families: A family includes the owner or renter of the home along with everyone related to them - whether through birth, marriage, or adoption. This includes relatives like spouses, children, parents, siblings, grandparents, and any other family members.
Households: A household includes all the people who occupy a housing unit (such as a house or apartment) as their usual place of residence.
Non Families: A nonfamily household is either someone living alone or when the owner/renter lives with people they aren't related to, like roommates.
Name
Median
Mean
Married Families$247,888-
Families$226,389$254,559
Households$210,100$235,424
Non Families-$140,209

$104,750

Average Income

$210,100

Median Household Income

2.85%

Poverty Rate

Nearby Cities

Sources

  1. US Census State Population Estimates - Most recent state estimates from the Census Bureau's Population Estimates Program
  2. US Census County Population Estimates - Most recent county estimates from the Census Bureau's Population Estimates Program
  3. American Community Survey (2009 - 2013)
  4. Census QuickFacts
  5. Historical Populations of States and Counties (1790 - 1990)