Mercer County, New Jersey

Mercer County population, land area and income

Mercer County had 392,138 residents in the Census Vintage 2024 estimate, on 224.5 square miles of land. It ranks 12th of 21 in New Jersey by population and 16th by land area. That works out to 1,746.9 people per square mile, 18.1 times the US average of 96.3, and in the top tenth nationally.

The median county-equivalent in New Jersey has 475,515 residents; Mercer County is somewhat smaller.

Its SAIPE 2023 median household income of $95,502 is in the top tenth among 3,143 counties with an estimate.

How Mercer County's population changed since 2020

Mercer County gained 5,646 residents between the July 2020 and July 2024 estimates, a rise of 1.5%. That ranks 17th of 21 in New Jersey for growth. The median New Jersey county changed by +2.3%, and the state as a whole by +2.5%.

Since the April 2020 estimates base, Mercer County recorded 17,392 births and 14,314 deaths, a natural change of +3,078. Net international migration added +18,320 and net domestic migration, people moving to or from other US counties, came to -16,678. The largest single component was international migration, which added 18,320 people.

Where Mercer County is

The Census internal point of Mercer County is at 40.282500, -74.703700. It sits in UTM zone 18N. The map shades New Jersey's 21 county-equivalents by population change from 2020 to 2024, darker for faster growth, with Mercer County outlined. Dots are towns of 1,000+ people with residents in it.

Towns in Mercer County

5 incorporated places of 1,000+ people have residents in Mercer County, 133,460 people together, or 34% of the county. Each figure counts only the part of the town inside Mercer County; towns marked "part" extend into another county. The largest is Trenton with 91,193.

Counties bordering Mercer County

The Census 2024 county adjacency file lists 6 neighbors for Mercer County, including 1 across a state line. The most populous is Middlesex County, NJ, with 890,119 residents. Distances run between Census internal points in a straight line.

• Middlesex County

  890,119 people

  19 mi NE

• PA

  Bucks County, PA

  650,131 people

  22 mi W

• Monmouth County

  647,520 people

  29 mi E

• Burlington County

  475,515 people

  28 mi S

• Somerset County

  357,467 people

  20 mi NNE

• Hunterdon County

  131,708 people

  22 mi NNW

Distance to Trenton and the nearest big city

Trenton is 5.1 miles SSW of Mercer County's internal point in a straight line. The nearest place of 100,000 or more is Philadelphia, PA (population 1,573,916), 29.5 miles away. The nearest place of 10,000 or more is Trenton, NJ (population 91,193), 5.2 miles away.

Mercer County FIPS code

The FIPS code of Mercer County is 34021: state code 34 for New Jersey plus county code 021. Use it as text, with the leading zero, when joining Census, BLS, or CDC county tables. SAIPE lists its 2023 median household income as $95,502.