Greenlawn is a hamlet and census-designated place (CDP) in Suffolk County, New York, United States. Located on Long Island in the Town of Huntington, the population was 13,742 at the 2010 census. Students primarily attend the Harborfields Central School District.
Originally known as Old Fields, it became known by the name Greenlawn with the coming of the Long Island Rail Road in 1870 or 1871. The LIRR chose the name Greenlawn for its station, apparently to project an idyllic rural/suburban image and foster resort travel to the beaches in Centerport. Greenlawn was well known for its pickle production during the 19th century as well as, to a lesser degree, potato and cabbage farms; the principal commodity, pickles, is still celebrated by the annual Pickle Festival, held by the local Greenlawn-Centerport Historical Association at the John Gardiner Farm. The Gardiner family was the first to make a name for themselves as pickle farmers in the region but a former slave, Samuel Ballton, earned the moniker "The Pickle King" for becoming a prolific pickle farmer in Greenlawn in the early 1900s.
Greenlawn is located at 40°51′28″N 73°21′57″W (40.857648, -73.365932).
According to the United States Census Bureau, the census-designated place (CDP) has a total area of 3.7 square miles (9.6 km2), all land.
As of the census of 2010, there were 13,742 people, 4,560 households, and 3,345 families residing in the CDP. The population density was 3,714.1 per square mile (1,446.5/km²). There were 4,722 housing units at an average density of 1,276.2/sq mi (497.1/km²). The racial makeup of the CDP was 74.0% White, 13.9% African American, 0.4% Native American, 4.1% Asian, 0.01% Pacific Islander, 4.9% some other race, and 2.7% from two or more races.