Suffolk County ( ) is the easternmost county in the U.S. state of New York, constituting the eastern two-thirds of Long Island. Suffolk is bordered to its west by Nassau County, to its east by Gardiners Bay and the open Atlantic Ocean, to its north by Long Island Sound, and to its south by the Atlantic Ocean.
As of the 2020 United States census, Suffolk County's population was 1,525,920, its highest decennial count ever, making Suffolk the fourth-most populous county in the State of New York and the most populous outside of the boroughs of New York City. Its county seat is Riverhead, though most county offices are in Hauppauge. The county was named after the county of Suffolk in England, the origin of its earliest European settlers.
Suffolk County incorporates the easternmost extreme of both the New York City metropolitan area and New York State. The geographically largest of Long Island's four counties and the second-largest of New York's 62 counties, Suffolk County is in length and in width at its widest (including water).About Suffolk County on the county website Most of the island is near sea level, with over of coastline.
Like other parts of Long Island, the county's high population density and proximity to New York City has resulted in a diverse economy, including industry, science, agriculture, fishery, and tourism. Housing affordability has become a significant concern in Suffolk County, as the median home price has climbed above US$760,000. Prominent scientific research facilities in Suffolk County include Brookhaven National Laboratory in Upton and Plum Island Animal Disease Center on Plum Island. The county is home to Stony Brook University in Stony Brook and Farmingdale State College in East Farmingdale.
History Suffolk County was part of the Connecticut Colony before becoming an original county of the province of New York, one of twelve created in 1683. From 1664 until 1683, it had been the East Riding of Yorkshire. Its boundaries were essentially the same as at present, with only minor changes in the boundary with its western neighbor, which was originally Queens County but has been Nassau County since the separation of Nassau from Queens in 1899.
During the American Revolutionary War, Great Britain occupied Suffolk County after the retreat of George Washington's forces in the Battle of Long Island, and the county remained under occupation until the British evacuation of New York on November 25, 1783.
According to the Suffolk County website, the county is the leading agricultural county in the state of New York, saying that: "The weather is temperate, clean water is abundant, and the soil is so good that Suffolk is the leading agricultural county in New York State. That Suffolk is still number one in farming, even with the development that has taken place, is a tribute to thoughtful planning, along with the excellent soil, favorable weather conditions, and the work of the dedicated farmers in this region."http://www.co.suffolk.ny.us/ "About Suffolk County"
Geography According to the U.S. Census Bureau, the county has an area of , of which is land and (62%) is water. It is the second-largest county in New York by total area and occupies 66% of the land area of Long Island.
Suffolk County occupies the central and eastern part of Long Island, in the extreme east of the State of New York. The eastern end of the county splits into two peninsulas, known as the North Fork and the South Fork. The county is surrounded by water on three sides, including the Atlantic Ocean and Long Island Sound, with of coastline. The eastern end contains large bays.
The highest elevation in the county, and on Long Island as a whole, is Jayne's Hill in West Hills, at above sea level. A low-lying coastal geography overall has led to Sufflok County incorporating shoreline resilience strategies related to sea level rise into urban planning.
Climate Suffolk County sits at the convergence of climate zones including the humid continental (Dfa) and humid subtropical (Cfa), bordering closely on an oceanic climate (Cfb). The majority of the county by land area is in the Dfa zone. Summers are cooler at the East end than in the western part of the county. The hardiness zone is 7a, except in Copiague Harbor, Lindenhurst, and Montauk, where it is 7b. Average monthly temperatures in Hauppauge range from in January to in July, and in the Riverhead town center they range from in January to in July, which includes both daytime and nighttime temperatures. On February 23, 2026, Central Islip in Suffolk County was besieged by 31 inches of snow, making it the largest single-day snowfall on record in Suffolk.
Adjacent counties Suffolk County has maritime boundaries with five other U.S. counties and is connected by land only to Nassau County. Nassau County—west Fairfield County, Connecticut—northwest New Haven County, Connecticut—north Middlesex County, Connecticut—north New London County, Connecticut—north Washington County, Rhode Island—northeast
National protected areas Amagansett National Wildlife Refuge Conscience Point National Wildlife Refuge Elizabeth A. Morton National Wildlife Refuge Fire Island National Seashore Sayville National Wildlife Refuge Seatuck National Wildlife Refuge Target Rock National Wildlife Refuge Wertheim National Wildlife Refuge
Demographics
Race and ethnicity +Suffolk County, New York – Racial and ethnic compositionRace / Ethnicity (NH = Non-Hispanic)Pop 1980Pop 1990Pop 2000Pop 2010 Pop 2020% 1980% 1990% 2000% 2010% 2020White alone (NH)1,141,0001,130,6941,118,4051,068,728967,33088.85%85.54%78.80%71.57%63.39%Black or African American alone (NH)69,55877,30393,262102,117107,2685.42%5.85%6.57%6.84%7.03%Native American or Alaska Native alone (NH)1,9662,5922,9812,9063,1020.15%0.20%0.21%0.19%0.20%Asian alone (NH)10,29722,41534,35550,29565,0190.80%1.70%2.42%3.37%4.26%Native Hawaiian or Pacific Islander alone (NH)xincluded in the Asian category in the 1980 Censusxincluded in the Asian category in the 1990 Census260275241xx0.02%0.02%0.02%Other race alone (NH)2,7211,0082,2173,0419,4790.21%0.08%0.16%0.20%0.62%Mixed race or Multiracial (NH)xnot an option in the 1980 Censusxnot an option in the 1990 Census18,47819,74940,522xx1.30%1.32%2.66%Hispanic or Latino (any race)58,68987,852149,411246,239332,9594.57%6.65%10.53%16.49%21.82%Total1,284,2311,321,8641,419,3691,493,3501,525,920 100.00%100.00%100.00%100.00%100.00%
2010 census According to the 2010 U.S. census there were 1,493,350 people and 569,985 households residing in the county. The census estimated Suffolk County's population decreased slightly to 1,481,093 in 2018, representing 7.5% of the census-estimated New York State population of 19,745,289Kings County (Brooklyn Borough), New York; Queens County (Queens Borough), New York; Nassau County, New York; Suffolk County, New York; New York QuickFacts Accessed February 12, 2020. and 19.0% of the census-estimated Long Island population of 7,869,820. The population density in 2010 was , with 569,985 households at an average density of . However, by 2012, with an estimated total population increasing moderately to 1,499,273 there were 569,359 housing units.http://quickfacts.census.gov/qfd/states/36/36103.html U.S. Census, estimate for 2012, January 6, 2014 As of 2006, Suffolk County was the 21st-most populous county in the United States.
By 2014, the county's racial makeup was estimated at 85.2% White, 8.3% African American, 0.6% Native American, 4.0% Asian, 0.1% Pacific Islander, and 1.8% from two or more races. Those identifying as Hispanic or Latino, of any race, were 18.2% of the population. Those who identified as "white alone", not being of Hispanic or Latino origin, represented 69.3% of the population. In 2006, the county's racial or ethnic makeup was 83.6% White (75.4% White Non-Hispanic). African Americans were 7.4% of the population. Asians stood at 3.4% of the population. 5.4% were of other or mixed race. Latinos were 13.0% of the population. In 2007, Suffolk County's most common ethnicities were Italian (29.5%), Irish (24.0%), and German (17.6%).
In 2002, The New York Times cited a study by the non-profit group ERASE Racism, which determined Suffolk and its neighboring county, Nassau, to be the most racially segregated suburbs in the United States.
In 2006, there were 469,299 households, of which 37.00% had children under the age of 18 living with them, 62.00% were married couples living together, 10.80% had a female householder with no husband present, and 23.20% were non-families. 18.30% of all households were made up of individuals, and 7.80% had someone living alone who was 65 years of age or older. The average household size was 2.96 and the average family size was 3.36.
In the county, the population was spread out, with 26.10% under the age of 18, 7.60% from 18 to 24, 31.20% from 25 to 44, 23.30% from 45 to 64, and 11.80% who were 65 years of age or older. The median age was 36 years. For every 100 females, there were 95.90 males. For every 100 females age 18 and over, there were 92.80 males.
In 2008, Forbes magazine released its American Community Survey and named Suffolk County number 4 in its list of the top 25 richest counties in America. In 2016, according to Business Insider, the 11962 zip code encompassing Sagaponack, within Southampton, was listed as the most expensive in the U.S., with a median home sale price of $8.5 million.
The median income for a household in the county was $84,767, and the median income for a family was $72,112. Males had a median income of $50,046 versus $33,281 for females. The per capita income for the county was $26,577. Using a weighted average from 2009 to 2014 about 6.40% of the population were below the poverty line. In earlier censuses, the population below the poverty line included 2.70% of those under age 18 and 2.30% of those age 65 or over.
Racial groups, ethnicity, and religious groups on Long Islandcompared to state and nationPlace Population2010census %white %blackorAfricanAmerican %Asian %Other %mixedrace %Hispanic/Latinoof anyrace %Catholic % notaffiliated %Jewish %Protestant Estimateof % notreportingRaceEthnicityReligious groupsNassau County 1,339,53273.011.17.65.92.414.6 52917715Suffolk County1,493,35080.87.43.45.92.416.5 52217811Long Island Total(including Brooklyn and Queens)7,568,30454.720.412.39.33.220.5 401815720NY State19,378,10265.715.97.38.03.017.6 422091016USA308,745,53872.412.64.87.32.916.3 223722312Source for Race and Ethnicity: 2010 CensusAmerican Indian, Native Alaskan, Native Hawaiian, and Pacific Islander make up just 0.5% of the population of Long Island, and have been included with "Other".Source for religious groups: ARDA2000 Churches were asked for their membership numbers. ARDA estimates that most of the churches not reporting were black Protestant congregations.
Law and government
Active Voter Registration and Party Enrollment as of February 20, 2026 Party Number of voters Percentage Democratic 371,050 32.74% Republican 356,218 31.43% Unaffiliated 350,168 30.90% Conservative 21,675 1.91% Working Families 4,415 0.39% Other 29,680 2.62% Total 1,133,206 100% +County officials Position Name Party Term Sheriff Errol D. Toulon Jr. Dem 2018–present District Attorney Raymond A. Tierney Rep 2022–present County Clerk Vincent A. Puleo Rep 2023–present Comptroller John M. Kennedy Jr. Rep 2015–present
State Senate Officials for Suffolk County District Senator Party 1 Anthony Palumbo Republican 2 Mario Mattera Republican 3 L. Dean Murray Republican 4 Monica Martinez Democratic 8 Alexis Weik Republican
State Assembly Officials for Suffolk County