County Maps US

Middlesex County, New Jersey

A county in New Jersey, ranked 3 of 21 by population.

CountyFIPS 34023

Within New Jersey
Middlesex County, highlighted, with the areas around it. Boundaries generalised from the 2025 Census cartographic boundary file; neighbour fills carry no data. The dot marks New Brunswick, the county seat, located via the 2025 Census Gazetteer.

Download SVGFull New Jersey map downloads

Population
883,335
+22,087 (+2.6%) since 2020
Land area
309.3
square miles. A further 4.2% of the total area is water
Population density
2,856
people per square mile, computed rather than published
County seat
New Brunswick
Seat of county government.
Established
1683
342 years ago
Largest city
New Brunswick city
Population 57,133.

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; Wikidata (CC0), Wikidata. Retrieved 30 August 2026.

Satellite view

Aerial imagery of Middlesex County with its boundary drawn on top. A map shows you the shape; this shows you what is inside it, and which side of the line a place falls on.

Aerial view of Middlesex County, New Jersey from the USGS National Map, with its boundary outlined
Imagery: USGS National Map, USGS Imagery Only, public domain, requested from USGS by your browser when you reach this point on the page, at 734 by 800 pixels. The boundary is the 2025 Census cartographic boundary file, reprojected to Web Mercator to match the imagery. You can also open the USGS National Map viewer.

Where Middlesex County ranks

Position among the 21 counties of New Jersey, and among all 3,144 US counties and county-equivalents. Computed from the figures on this page.

MeasureValueIn New JerseyNationally
Population883,3353rd of 2169th of 3,144
Land area309.3 sq mi12th of 212,787th of 3,144
Population density2,856 per sq mi5th of 2143rd of 3,144
Median household income$111,5497th of 2185th of 3,143

Full data for Middlesex County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population883,335Vintage 2025 Population Estimates
Population in 2020861,248Vintage 2025 Population Estimates
2020 estimates base?863,225Vintage 2025 Population Estimates
Land area309.3 sq mi2025 Gazetteer Files
Water area13.6 sq mi2025 Gazetteer Files
Total area322.9 sq mi2025 Gazetteer Files
Population density?2,856 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$111,549American Community Survey 2020-2024 5-Year Estimates
Median home value$462,900American Community Survey 2020-2024 5-Year Estimates
Median age39.5American Community Survey 2020-2024 5-Year Estimates
Households307,782American Community Survey 2020-2024 5-Year Estimates
Housing units317,979American Community Survey 2020-2024 5-Year Estimates

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026. Population density is computed here, not published: it divides the Vintage 2025 population estimate by the 2025 Gazetteer land area, which are two different Census products. Retrieved 30 August 2026.

How the population changed

The Census Bureau publishes the components behind an estimate, not just the total. For the year to July 2025:

Births minus deaths
+2,409
8,381 births, 5,972 deaths
Net migration
-699
More people moved out than moved in.

Source: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026. Retrieved 30 August 2026.

The 5 areas bordering Middlesex County

Ordered by the length of the border actually shared, which the Census Bureau publishes in its county adjacency file and which no other county reference presents.

Bordering areaStateShared borderPopulation
Somerset CountyNew Jersey25 mi356,486
Monmouth CountyNew Jersey23 mi651,035
Mercer CountyNew Jersey18 mi399,289
Union CountyNew Jersey16 mi601,863
Richmond CountyNew York11 mi501,290

Source: US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. Retrieved 30 August 2026.

Side by side

All 21 counties of New Jersey

Open the interactive New Jersey county map, or jump straight to any of them.

Data on this page last rebuilt 30 August 2026. How these figures are produced.