Middlesex County is a county located in the north-central part of the U.S. state of New Jersey, extending inland from the Raritan Valley region to the northern portion of the Jersey Shore. As of the 2020 United States census, the county was the state's third-most populous county with a population of 863,162, its highest decennial count ever and an increase of 53,304 (+6.6%) from the 2010 census count of 809,858, which in turn reflected an increase of 59,696 (8.0%) from the 750,162 counted in the 2000 census. Middlesex is part of the New York metropolitan area. Many communities within the county serve as commuter towns to and from New York City and other points north. The county is part of the Central Jersey region of the state.

The county is located in the middle of the Northeast megalopolis of the U.S. Its county seat is the city of New Brunswick, a center for the sciences, arts, and cultural activities, and the headquarters of the state's flagship academic institution, Rutgers University. The county's most populous place, with 107,588 residents as of the 2020 census, is Edison, while Monroe Township covers the largest area of any municipality, at 42.19 square miles (109.3 km). Since the 2010 census, the state's center of population is in East Brunswick; the center of population for New Jersey has been in Middlesex County since the 1900 census. 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. Middlesex County calls itself The Greatest County in the Land.

The county was primarily settled due to its optimal location along the Raritan River. Middlesex was originally formed as one of four administrative districts within Province of East Jersey in 1675, together with Bergen, Essex and Monmouth districts. Middlesex County was formed within East Jersey on March 7, 1683. The population increased so the county was partitioned on October 31, 1693, into the townships of Piscataway, Perth Amboy, and Woodbridge. Adjacent Somerset County was established on May 14, 1688, created from portions of Middlesex County.

The county's first court met in June 1683 in Piscataway, and held session at alternating sites over the next century in Perth Amboy, Piscataway, and Woodbridge before relocating permanently to New Brunswick in 1778. 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). Middlesex County is most demographically notable as the U.S. county with the highest concentration of Asian Indians, at nearly 20% in 2020, spanning the county's boundaries between Little India, Edison/Iselin in the north and Monroe Township at its southern tip.

Middlesex has a hot-summer humid continental climate (Dfa) which borders a humid subtropical climate (Cfa) on Raritan Bay and Arthur Kill. Average monthly temperatures in downtown New Brunswick range from 31.9 °F (−0.1 °C) in January to 75.6 °F (24.2 °C) in July, while in South Amboy they range from 32.3 °F (0.2 °C) in January to 75.9 °F (24.4 °C) in July. In recent years, average temperatures in the county seat of New Brunswick have ranged from a low of 22 °F (−6 °C) in January to a high of 86 °F (30 °C) in July, although a record low of −13 °F (−25 °C) was recorded in January 1984 and a record high of 103 °F (39 °C) was recorded in July 1999. Average monthly precipitation ranged from 2.98 inches (76 mm) in February to 5.08 inches (129 mm) in July.

According to the U.S. Census Bureau, as of the 2020 Census, the county had a total area of 322.87 square miles (836.2 km), of which 309.22 square miles (800.9 km) was land (95.8%) and 13.65 square miles (35.4 km) was water (4.2%). The county is named after the historic English county of Middlesex.

Bisected by the Raritan River, the county is topographically typical of Central Jersey in that it is largely flat. The majority of the county is located on the inner coastal plain, with the remainder of the county being located on the Eastern Piedmont. The elevation ranges from sea level to 300 feet (91 m) above sea level on a hill scaled by Major Road/ Sand Hill Road near Route 1 in South Brunswick Township.

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. The area includes peaks of over 200 feet.

New Brunswick, New Jersey
Climate chart (explanation)
J F M A M J J A S O N D     3.6     39 22     3     43 24     4.2     51 30     4.2     62 40     4.2     72 50     4.4     81 60     5.1     86 65     4.2     84 64     4.5     77 55     3.8     66 43     3.8     55 36     4.1     44 27 █ Average max. and min. temperatures in °F █ Precipitation totals in inches Source: The Weather Channel
Metric conversion J F M A M J J A S O N D     92     4 −6     76     6 −4     106     11 −1     107     17 4     106     22 10     112     27 16     129     30 18     105     29 18     115     25 13     97     19 6     97     13 2     103     7 −3 █ Average max. and min. temperatures in °C █ Precipitation totals in mm

Historical population

Census	Pop.	Note	%±
1790	15,956		—
1800	17,890		12.1%
1810	20,381		13.9%
1820	21,470		5.3%
1830	23,157		7.9%
1840	21,893	*	−5.5%
1850	28,635		30.8%
1860	34,812		21.6%
1870	45,029		29.3%
1880	52,286		16.1%
1890	61,754		18.1%
1900	79,762		29.2%
1910	114,426		43.5%
1920	162,334		41.9%
1930	212,208		30.7%
1940	217,077		2.3%
1950	264,872		22.0%
1960	433,856		63.8%
1970	583,813		34.6%
1980	595,893		2.1%
1990	671,780		12.7%
2000	750,162		11.7%
2010	809,858		8.0%
2020	863,162		6.6%
2023 (est.)	863,623		0.1%
Historical sources: 1790-1990 1970-2010 2000 2010 2020 * = Lost territory in previous decade.

Middlesex County is prominently known for its significant concentration of Indians. The growing Little India is a Desi-focused commercial strip in Middlesex County, the U.S. county with the highest concentration of Indians. The Oak Tree Road strip runs for about one-and-a-half miles through Edison and neighboring Iselin in Woodbridge Township, near the area's sprawling Chinatown and Koreatown, running along New Jersey Route 27. It is the largest and most diverse Desi cultural hub in the United States. 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, 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. Carteret's Punjabi Sikh community, variously estimated at upwards of 3,000, is the largest concentration of Sikhs in New Jersey. In Middlesex County, election ballots are printed in English, Spanish, Gujarati, Hindi, and Punjabi.

Along with other counties in New Jersey, Middlesex is also home to a large Jewish community, especially Orthodox. The world's largest Jewish gathering outside of Israel occurred in Edison on December 1, 2024.

As of the Census of 2020, the county had 863,162 people, 285,906 households, and 209,808 families. The population density was 2,794 inhabitants per square mile (1,078.8/km). There were 315,521 housing units at an average density of 1,021.4 per square mile (394.4/km). The county's racial makeup was 41.9% White, 9.8% African American, 0.53% Native American, 26.5% Asian, and 9.06% from two or more races. Hispanic or Latino of any race were 22.4% of the population.

There were 285,906 households, of which 34.6% had children under the age of 18 living with them, 56.9% were married couples living together, 24.2% had a female householder with no husband present, 14.2% had a male householder with no wife present and 26.6% were non-families. 14.8% of all households were made up of individuals, and 10.8% had someone living alone who was 65 years of age or older. The average household size was 2.80 and the average family size was 3.32.

About 21.6% of the county's population was under age 18, 9.3% was from age 18 to 24, 40.1% was from age 15 to 44, and 15.5% was age 65 or older. The median age was 39.3 years. The gender makeup of the county was 49.4% male and 50.5% female. For every 100 females, there were 97.8 males.

The county's median household income was $93,418, and the median family income was $107,149. About 8.8% of the population were below the poverty line, including 11.1% of those under age 18 and 8.8% of those age 65 or over.

The 2010 United States census counted 809,858 people, 281,186 households, and 203,016 families in the county. The population density was 2,621.6 per square mile (1,012.2/km). There were 294,800 housing units at an average density of 954.3 per square mile (368.5/km). The racial makeup was 58.60% (474,589) White, 9.69% (78,462) Black or African American, 0.34% (2,777) Native American, 21.40% (173,293) Asian, 0.03% (251) Pacific Islander, 6.99% (56,569) from other races, and 2.95% (23,917) from two or more races. Hispanic or Latino of any race were 18.40% (148,975) of the population.

Of the 281,186 households, 34.4% had children under the age of 18; 55.9% were married couples living together; 11.8% had a female householder with no husband present and 27.8% were non-families. Of all households, 22.5% were made up of individuals and 8.9% had someone living alone who was 65 years of age or older. The average household size was 2.8 and the average family size was 3.29.

22.9% of the population were under the age of 18, 10.2% from 18 to 24, 28.3% from 25 to 44, 26.3% from 45 to 64, and 12.3% who were 65 years of age or older. The median age was 37.2 years. For every 100 females, the population had 96.4 males. For every 100 females ages 18 and older there were 94 males.

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.

Major non-governmental employers in Middlesex County include the following, grouped by ranges of employees:

• 9,010: Rutgers University
• 5,000 – 5,249: Robert Wood Johnson University Hospital
• 3,500 – 3,749: Bristol-Myers Squibb, Wakefern Food Corporation
• 3,000 – 3,249: Merrill Lynch, Novo Nordisk
• 2,750 – 2,999: Johnson & Johnson, Prudential Insurance Company, Silverline Building Products, St. Peter's University Hospital, Telcordia Technologies
• 2,500 – 2,749: JFK Medical Center, Raritan Bay Medical Center
• 2,000 – 2,249: Pathmark
• 1,750 – 1,999: Home Depot, United Parcel Service
• 1,500 – 1,749: Hess Corporation, Dow Jones & Company, Siemens
• 1,250 – 1,499: AT&T, BASF (formerly Engelhard)
• 1,000 – 1,249: Aetna, Fujitsu, Prudential
• Undisclosed: Canon, Japanese company specializing in imaging products.

Middlesex County is named after the county of the same name in England.

Middlesex County is governed by a Board of Commissioners, which is comprised of seven members who are elected at-large on a partisan basis to serve three-year terms of office on a staggered basis, with either two or three seats coming up for election each year as part of the November general election. At an annual reorganization meeting held in January, the board selects from among its members a Commissioner Director and deputy director. The Commissioner Director appoints commissioners to serve as chairpersons and members on the various committees which oversee county departments. Middlesex County also elects three "constitutional officers" whose existence is laid out in the New Jersey Constitution. The County Clerk and Surrogate serve five-year terms and the Sheriff serves a three-year term of office. In 2016, freeholders were paid $23,438 and the freeholder director was paid an annual salary of $24,428, though Ronald Rios has accepted a salary of $8,340 as director.

As of 2025, Middlesex County's Commissioners (with terms for director and deputy ending every December 31) are:

Commissioner	Party, Residence, Term
Director Ronald G. Rios	D, Carteret, 2027
Deputy Director Shanti Narra	D, North Brunswick, 2027
Claribel A. "Clary" Azcona-Barber	D, New Brunswick, 2025
Charles Kenny	D, Woodbridge Township, 2025
Leslie Koppel	D, Monroe Township, 2026
Chanelle Scott McCullum	D, Piscataway, 2025
Charles E. Tomaro	D, Edison, 2026

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." These officers are the County Clerk and County Surrogate (both elected for five-year terms of office) and the County Sheriff (elected for a three-year term). Middlesex county's constitutional officers are:

Title	Representative
County Clerk	Nancy Pinkin (D, East Brunswick, 2025)
Sheriff	Mildred S. Scott (D, Piscataway, 2025)
Surrogate	Claribel Cortes (D, North Brunswick, 2026)

Republicans have not won countywide in Middlesex County since 1991. The Middlesex County Prosecutor has been Yolanda Ciccone since June 2020. Middlesex County constitutes Vicinage 8 of the New Jersey Superior Court; the vicinage is seated at the Middlesex County Courthouse, at 56 Paterson Street in New Brunswick. The Middlesex Vicinage also has facilities for the Family Part at the Middlesex County Family Courthouse at 120 New Street, also in New Brunswick; there are also other facilities in New Brunswick and Perth Amboy for Probation. The Assignment Judge for Vicinage 8 is Alberto Rivas.

The 6th and 12th congressional districts cover the county. For the 118th United States Congress, New Jersey's 6th congressional district is represented by Frank Pallone (D, Long Branch). For the 118th United States Congress, New Jersey's 12th congressional district is represented by Bonnie Watson Coleman (D, Ewing Township).

The 25 municipalities of Middlesex County are part of seven legislative districts.

District	Senator	Assembly	Municipalities
12th	Owen Henry (R)	Alex Sauickie (R) Robert D. Clifton (R)	Helmetta, Old Bridge, and Spotswood. The remainder of this district covers portions of Burlington County, Monmouth County and Ocean County.
14th	Linda R. Greenstein (D)	Wayne DeAngelo (D) Tennille McCoy (D)	Cranbury Township, Jamesburg, Monroe Township, and Plainsboro. The remainder of this district covers portions of Mercer County.
16th	Andrew Zwicker (D)	Mitchelle Drulis (D) Roy Freiman (D)	South Brunswick. The remainder of this district covers portions of Hunterdon County, Mercer County, and Somerset County.
17th	Bob Smith (D)	Kevin Egan (D) Joseph Danielsen (D)	New Brunswick, North Brunswick, and Piscataway. The remainder of this district covers portions of Somerset County.
18th	Patrick J. Diegnan (D)	Robert Karabinchak (D) Sterley Stanley (D)	East Brunswick, Edison, Highland Park, Metuchen, Milltown, South Plainfield, and South River.
19th	Joe F. Vitale (D)	Craig Coughlin (D) Yvonne Lopez (D)	Carteret, Perth Amboy, Sayreville, South Amboy, and Woodbridge.
21st	Jon Bramnick (R)	Nancy Munoz (R) Michele Matsikoudis (R)	Dunellen and Middlesex Borough. The remainder of this district covers portions of Somerset County, Morris County, and Union County.

Thomas N. Acken served as the sheriff in 1891. Joseph Spicuzzo served in 2014 and was arrested for bribery. Mildred S. Scott is the current county sheriff, she was sworn in on January 1, 2011, as the first female sheriff of Middlesex County and the first African-American sheriff in the state of New Jersey.

After being a Republican stronghold in the late 19th and early 20th centuries, Middlesex County leaned Democratic for much of the 20th century beginning with Franklin Roosevelt's victory in the county in 1932. Throughout the twentieth century, in close elections, the county would always vote Democratic, sometimes by solid margins, but the county was willing to flip Republican in the midst of nationwide Republican landslides in the 1970s and 1980s. Since 1992, the county has always voted Democratic, however, the 2024 election saw the Democratic margin held to the single digits for the first time since 1992. As of August 1, 2020, there were a total of 545,795 registered voters in Middlesex County, of which 229,982 (42.1%) were registered as Democrats, 84,258 (15.4%) were registered as Republicans and 224,058 (41.1%) were registered as Unaffiliated. There were 7,497 (1.4%) voters registered to other parties.

United States presidential election results for Middlesex County, New Jersey

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	162,459	44.31%	191,802	52.31%	12,378	3.38%
2020	143,467	38.19%	226,250	60.22%	5,975	1.59%
2016	122,953	37.42%	193,044	58.76%	12,560	3.82%
2012	107,310	35.55%	190,555	63.13%	3,995	1.32%
2008	123,695	38.43%	193,812	60.21%	4,367	1.36%
2004	126,492	42.76%	166,628	56.33%	2,685	0.91%
2000	93,545	36.14%	154,998	59.88%	10,306	3.98%
1996	82,433	31.90%	145,201	56.20%	30,752	11.90%
1992	108,701	38.10%	128,824	45.16%	47,746	16.74%
1988	143,422	54.30%	117,149	44.35%	3,548	1.34%
1984	160,221	59.82%	104,905	39.17%	2,727	1.02%
1980	122,354	50.73%	97,304	40.34%	21,548	8.93%
1976	113,539	47.14%	122,859	51.01%	4,466	1.85%
1972	149,033	61.41%	88,397	36.42%	5,264	2.17%
1968	96,515	42.79%	103,339	45.82%	25,676	11.38%
1964	63,370	29.39%	151,196	70.12%	1,052	0.49%
1960	83,025	41.60%	116,095	58.18%	436	0.22%
1956	100,071	60.54%	64,538	39.05%	677	0.41%
1952	73,577	50.32%	70,234	48.03%	2,413	1.65%
1948	49,810	42.86%	61,634	53.04%	4,766	4.10%
1944	45,232	42.12%	60,504	56.35%	1,642	1.53%
1940	41,709	38.26%	67,140	61.59%	164	0.15%
1936	32,959	34.57%	61,679	64.69%	702	0.74%
1932	32,673	40.45%	45,997	56.94%	2,111	2.61%
1928	38,714	52.35%	34,908	47.20%	328	0.44%
1924	34,556	62.28%	16,373	29.51%	4,553	8.21%
1920	29,334	69.70%	11,618	27.60%	1,136	2.70%
1916	11,851	53.51%	9,975	45.04%	320	1.44%
1912	4,743	25.78%	8,186	44.49%	5,470	29.73%
1908	11,270	57.51%	7,966	40.65%	359	1.83%
1904	10,117	57.22%	6,996	39.57%	569	3.22%
1900	9,347	55.19%	7,191	42.46%	399	2.36%
1896	9,304	58.73%	5,976	37.72%	563	3.55%

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Middlesex County hosts various county roads, state routes, US routes, and interstate highways, as well as toll highways. As of May 2010, the county had a total of 2,584.38 miles (4,159.16 km) of roadways, of which 2,118.08 miles (3,408.72 km) were maintained by the municipality, 292.16 miles (470.19 km) by Middlesex County and 131.48 miles (211.60 km) by the New Jersey Department of Transportation, 41.49 miles (66.77 km) by the New Jersey Turnpike Authority and 1.17 miles (1.88 km) by the Port Authority of New York and New Jersey.

County roads include CR 501, CR 514, CR 516 (only in Old Bridge), CR 520 (only in Old Bridge), CR 522, CR 527, CR 529, CR 531, CR 535, and CR 539 (only in Cranbury).

The state routes are: Route 18, Route 26 (only in North Brunswick – entirely concurrent with Livingston Avenue), Route 27, Route 28, Route 32, Route 33 (only in Monroe Township), Route 34 (only in Old Bridge), Route 35, Route 91 (concurrent with Jersey Avenue in North Brunswick and entering New Brunswick), Route 171, Route 172 (only in New Brunswick), Route 184 and Route 440.

U.S. Routes include: Route 1, Route 9, Route 1/9 (only in Woodbridge) and Route 130.

The county also includes some limited access highways and Interstates as well. 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). The New Jersey Turnpike carries I-95 through the center of the county. The Turnpike has five interchanges in Middlesex County: Exit 12 in Carteret, Exit 11 in Woodbridge, Exit 10 in Edison, Exit 9 in East Brunswick and Exit 8A in Monroe Township.

The New Jersey Department of Transportation is upgrading the Route 18 "avenue" to a freeway between the Route 1 interchange all the way up to the new 18 Extension in Piscataway.

The Turnpike Authority planned to build Route 92, which was to start near the intersection of Ridge Road & Route 1 in South Brunswick to Interchange 8A in Monroe Township. This plan was cancelled on December 1, 2006.

The southern end of the "dual-dual" configuration (inner car lanes and outer truck lanes) used to be one mile south of Interchange 8A at the border of Cranbury and Monroe Township. It was relocated to Exit 6 in Mansfield Township in Burlington County after the Turnpike widening project was completed in early November 2014.

NJ Transit provides Middlesex County with frequent commuter rail service along the North Jersey Coast Line, Northeast Corridor Line, and Raritan Valley Line. The North Jersey Coast Line runs through the eastern part of the county. The Northeast Corridor Line runs through the northern and central part of the county. The Raritan Valley Line serves Dunellen and is accessible to other communities along the county's northern border with Union and Somerset counties.

Intercity rail service is provided by Amtrak. 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. The Acela service also occasionally stops at Metropark.

Bus service in Middlesex County is provided by New Jersey Transit, Coach USA's Suburban Transit, the extensive Rutgers Campus bus network, the MCAT shuttle system, and DASH buses. There are bus routes that serve all townships in the county on weekdays, and studies are being conducted to create the New Brunswick Bus Rapid Transit system.

• Middlesex County College (Edison – main campus; New Brunswick, Perth Amboy)
• Rutgers University New Brunswick Campus (New Brunswick, Piscataway)
• Rutgers Biomedical and Health Sciences (New Brunswick)
• Princeton University – Forrestal Campus (Plainsboro)
• DeVry University (North Brunswick)
• Chamberlain University (North Brunswick)
• New Brunswick Theological Seminary (New Brunswick Campus)

School districts, all PreK/K-12 (except as indicated), include:

The county offers more than 1,900 inpatient beds among five major hospitals.

Hospitals

Hospital	Town	Type	Beds	Health Network
JFK Medical Center	Edison	Acute	498	Hackensack Meridian Health
PSE&G Children's Specialized Hospital	New Brunswick	Pediatric Rehabilitation	140	RWJBarnabas Health
Raritan Bay Medical Center (Old Bridge)	Old Bridge	Acute	113	Hackensack Meridian Health
Raritan Bay Medical Center (Perth Amboy)	Perth Amboy	Acute	388	Hackensack Meridian Health
Robert Wood Johnson University Hospital	New Brunswick	Major Teaching	465	RWJBarnabas Health
The Bristol-Myers Squibb Children's Hospital	New Brunswick	Acute Pediatric	105	RWJBarnabas Health
Rutgers Cancer Institute of New Jersey	New Brunswick	Research, Cancer		RWJBarnabas Health
St. Peter's University Hospital	New Brunswick	Acute Teaching	478	Saint Peters HCS
Penn Medicine Princeton Medical Center	Plainsboro	Acute Teaching	305	Penn Medicine