East Islip is a census-designated place (CDP) and a hamlet located in the Town of Islip on unincorporated land in Suffolk County, New York. As of the 2000 census, the CDP had only 4,578 households and a total population of 14,078 persons.
Originally referred to as "east of Islip," the proper name was acquired in 1890 from the estate of William Nicoll, an English aristocrat who purchased the hamlet on the 29th of November 1693 to erect a family residence. Nicolls purchase comprised of 51,000 acres (210 km²) from the Secatogues Indians including territory reaching east to Bayport, west to Babylon, and north to Lake Ronkonkoma. His mansion, Islip Grange named after his family's ancestral estate at Northampshire, England stood on the shoreline of the current Heckscher State Park, referred to as Nicolls Neck. East Islip and neighboring Islip, Bay Shore, Great River and Oakdale, were mansion-heavy enclave on Long Island's South Shore, home to world renowned families of nobility and old money.
Today, the hamlet is no longer a haven to New York and the world's social elite. What remains are much smaller, yet exclusive and wealthy communities and few larger estates. Many of these newer communities were built on the land belonging to former estates that were sold off; most notably the estate of Percy G. Williams. The Moorings, an opulent waterfront guard-gated private community is one of the hamlet's premier neighborhoods and highly regarded by Long Island's affluent. Other neighborhoods within the hamlet include Deer Run and Percy Williams Cove.
According to the United States Census Bureau, the CDP has a total area of 4.4 square miles (11.3 km²), of which, 4.1 square miles (10.6 km²) of it is land and 0.2 square miles (0.6 km²) of it (5.73%) is water.
There were 4,578 households out of which 42.9% had children under the age of 18 living with them, 68.0% were married couples living together, 10.0% had a female householder with no husband present, and 18.5% were non-families. 15.2% of all households were made up of individuals and 7.3% had someone living alone who was 65 years of age or older. The average household size was 3.03 and the average family size was 3.38.
In the CDP the population was spread out with 28.5% under the age of 18, 6.3% from 18 to 24, 32.3% from 25 to 44, 21.1% from 45 to 64, and 11.8% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 95.2 males. For every 100 females age 18 and over, there were 90.1 males.
The median income for a household in the CDP was $71,106, and the median income for a family was $77,593. Males had a median income of $51,554 versus $36,959 for females. The per capita income for the CDP was $27,356. About 2.8% of families and 3.7% of the population were below the poverty line, including 4.3% of those under age 18 and 4.0% of those age 65 or over.