|Named for||Suffolk, England|
|• Executive||Steve Bellone (D)|
|• Total||2,373 sq mi (6,150 km2)|
|• Land||912 sq mi (2,360 km2)|
|• Water||1,461 sq mi (3,780 km2) 62%|
|• Density||1,637.0/sq mi (632.0/km2)|
|Time zone||UTC−5 (Eastern)|
|• Summer (DST)||UTC−4 (EDT)|
|Congressional districts||1st, 2nd, 3rd|
|Population is the official 2020 census count|
|Part of a series on|
Suffolk County (//) is the easternmost county in the U.S. state of New York. It is located on the Eastern end of Long Island. According to the 2020 United States census, the county's population was 1,525,920  making it the fourth-most populous county in New York State, after New York City's Brooklyn, Queens, and Manhattan. Its county seat is Riverhead, though most county offices are in Hauppauge. The county was named after the county of Suffolk in England, from where its earliest European settlers came.
Suffolk County incorporates the easternmost extreme of the New York City metropolitan area. The geographically largest of Long Island's four counties and the second-largest of 62 counties in New York State, Suffolk measures 86 miles (138 km) in length and 26 miles (42 km) in width at its widest (including water). Most of the island is near sea level, with over 1,000 miles of coastline.
Like other parts of Long Island, the high population density and relative closeness to New York City means that the economy has a mix of industry and science satellite to the city alongside more rural activities like agriculture, a fishery and tourism. Major scientific research facilities in Suffolk County include Brookhaven National Laboratory in Upton, Cold Spring Harbor Laboratory in Huntington, and Plum Island Animal Disease Center on Plum Island. The county is also home to several major universities such as Stony Brook University and Farmingdale State College.
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