Many communities within the county serve as commuter towns to and from New York City and other points north.

[11][12][13] The county is located in the middle of the Northeast megalopolis of the U.S. Its county seat is the city of New Brunswick,[2] a center for the sciences, arts, and cultural activities, and the headquarters of the state's flagship academic institution, Rutgers University.

[14] The county's most populous place, with 107,588 residents as of the 2020 census, is Edison,[15] while Monroe Township covers the largest area of any municipality, at 42.19 square miles (109.3 km2).

[17] Middlesex County hosts an extensive transportation network, including several rail stations along the heavily traveled Northeast Corridor Line of the New Jersey Transit commuter rail system, as well as the intersection of the New Jersey Turnpike and the Garden State Parkway, the state's two busiest motor vehicle roadways, in Woodbridge Township.

[19] The population increased so the county was partitioned on October 31, 1693, into the townships of Piscataway, Perth Amboy, and Woodbridge.

[20] Despite its status as a residential, commercial, and industrial stronghold and a centrally accessible transportation hub, Middlesex is also home to an extensive public park system with expansive greenways, totaling more than 6,300 acres (2,500 ha).

[24] Bisected by the Raritan River, the county is topographically typical of Central Jersey in that it is largely flat.

[25] Another area with higher elevation in the county is the Perth Amboy Moraine, left by the southern limit of the Laurentide Ice Sheet.

Only the far northeastern area of the county was glaciated, and the Perth Amboy Moraine stretches from Perth Amboy, through Woodbridge, Edison and Metutchen, and stradles the border of Edison and South Plainfield before exiting the county.

[32][33] Monroe Township in Middlesex County has experienced a particularly rapid growth rate in its Indian American population, with an estimated 5,943 (13.6%) as of 2017,[34] which was 23 times the 256 (0.9%) counted as of the 2000 Census; and Diwali is celebrated by the township as a Hindu holiday.

[35] In Middlesex County, election ballots are printed in English, Spanish, Gujarati, Hindi, and Punjabi.

[36] Along with other counties in New Jersey, Middlesex is also home to a large Jewish community, especially Orthodox.

[8] The Bureau of Economic Analysis calculated that the county's gross domestic product was $59.0 billion in 2021, which was ranked second in the state and was a 6.8% increase from the prior year.

[39] Major non-governmental employers in Middlesex County include the following, grouped by ranges of employees:[40][41] Clay was once frequently mined in Middlesex County,[42] with mining across the Raritan Formation continuing until the late twentieth century.

[48] As of 2025[update], Middlesex County's Commissioners (with terms for director and deputy ending every December 31) are:[44][49][50] Article VII Section II of the New Jersey State Constitution requires each county in New Jersey have three elected administrative officials known as "constitutional officers."

[68][69] For the 119th United States Congress, New Jersey's 6th congressional district is represented by Frank Pallone (D, Long Branch).

[70][71] For the 119th United States Congress, New Jersey's 12th congressional district is represented by Bonnie Watson Coleman (D, Ewing Township).

Robert D. Clifton (R) Tennille McCoy (D) Roy Freiman (D) Joseph Danielsen (D) Sterley Stanley (D) Yvonne Lopez (D) Michele Matsikoudis (R) Thomas N. Acken served as the sheriff in 1891.

Middlesex County hosts the southern end of I-287 which turns into Route 440 that connects to the Outerbridge Crossing.

The Garden State Parkway passes through the eastern part of the county, which features nine interchanges and the northern start/end of the split-roadways (Express & Local Lanes).

It was relocated to Exit 6 in Mansfield Township in Burlington County after the Turnpike widening project was completed in early November 2014.

The routes that run through Middlesex County are the Acela Express, Keystone, Northeast Regional, and Vermonter services, although only the Keystone and Northeast Regional have regular stops within Middlesex County, at either New Brunswick or Metropark station.

Bus service in Middlesex County is provided by New Jersey Transit, Coach USA's Suburban Transit, the extensive Rutgers Campus bus network,[96] the MCAT shuttle system,[97] and DASH buses.

Many of these areas are census-designated places that have been defined by the United States Census Bureau for enumeration purposes within a Township and for which 2010 population data is included in parentheses.