Matthias Nicoll relocated to New York from Islip, Northamptonshire, England, in 1664. His son, William Nicoll, became a royal patentee of the east end of what is now the Town of Islip, and his domain reached from East Islip to Bayport and included Sayville, West Sayville, Oakdale, Great River, Islip Terrace, Central Islip, Hauppauge, Holbrook, Bohemia, Brentwood, Holtsville and a portion of Ronkonkoma.

All of this land was bought from Winne-quaheagh, Sachem (chief) of Connetquot in 1683. The yearly fee paid to Governor Thomas Dongan of New York was five bushels of quality winter wheat or 25 shillings. Other early land patentees were Andrew Gibb (Islip Hamlet), John Mowbray (Bay Shore, originally Awixa), Stephan Van Cortlandt (Sagtikos Manor), and Thomas Willets (West Islip). By 1710, the colonial government passed an act to enable the precinct of Islip in the County of Suffolk to elect two assessors, a collector, a constable and a supervisor.

The people had a voice. Growth, however, remained at a standstill until the Revolutionary War ended when, in the 17 years that followed, there was more progress than in the 50 years preceding. This activity was partly due to the impact of American shipping. By 1825, it was necessary to install a Fire Island light across the Great South Bay and regular ferry service between Bay Shore and Fire Island began in 1862.

In 1867[?] the Long Island Rail Road came to Islip and the first depot was built. People were discovering Islip and the tourist trade soon took hold. Tourism brought much wealth into the area and business sprung up to service the hotels that began to dot the landscape. Some of those tourists stayed on and built summer homes, thus the vacationers and the town seemed to enjoy a mutual prosperity.

But the old guard was changing. Early in the 20th century, diesel-powered ferries replaced the whale boats while housing developments and small manufacturing firms sprang up on the sites of old farms. Like the rest of the country, Islip and all of Long Island suffered during the Stock Market Crash and the Great Depression.

When the veterans returned home from World War II, there was a housing shortage in New York City, but a rebirth on Long Island. Within a decade following the end of the war, Islip began to turn from a bucolic farming community into a bustling suburb, becoming what was once described as a "bedroom" of New York City.

The influx of people was tremendous - from 71,000 in 1950 to 280,000 in 1970. Then, as growth continued eastward on Long Island, the pace in Islip slowed. In 1987, the 430 tons of ash that resulted from incineration of the cargo of the Mobro 4000 "Garbage Barge" was added to the landfill in Islip. In response to the garbage barge incident, the Town of Islip developed Keep Islip Clean, WRAP, and other environmentally friendly initiatives to help bolster its image.

These acts resulted in one of the first comprehensive recycling programs in the United States.