In November of 1863, William Nicoll purchased 50,000 acres from Sachem (Chief) Winnequaheagh of the Connetquot tribe, and named it Islip Grange in honor of the town in England from which he emigrated. the original settlement encompassed Bayport, Bohemia, Brentwood, Central Islip, East Islip, Great River, Hauppauge, Holbrook, Holtsville, Islip Terrace, Oakdale, Sayville, West Sayville and part of Ronkonkoma; some of which is now the site of Heckscher State Park.

Some early settlers made their living raising grain and beef, but Islip’s proximity to the water made fishing and shipping the principle way of life. Jacob Ockers, whose Oakdale home on Montauk Highway is the only town-owned structure listed in the National Register of Historic Places, was know as “The Oyster King” at the turn of the century. By 1900, his Blue Point Oyster Company shipped as many as 100,000 barrels of oysters a year all over the world. In 1908, New York State passed a law forbidding any oysters to be called “Bluepoints” unless they came from the Great South Bay. The clam and oyster industry employed 500 boats and 1,100 men locally and oyster shells were used to pave the town streets until around 1915.

The Great South Bay also attracted wealthy tourists from New York City who built mansions, lodges and country clubs for their vacationing pleasure, some of which still stand today like Sagtikos Manor in West Bay Shore and St. John’s Episcopal Church in Oakdale. The William K. Vanderbilt estate in Oakdale was the site of Dowing College until last year and the estate of Admiral Bourne, founder of the Singer Sewing Machine Company, in Oakdale is now the site of St. John’s University. The original South Side Sportsman’s Lodge still stands amid the beautiful grounds of Connetquot River State Park.

Technically a hamlet within the Town of Islip, the name "Islip" was chosen by local residents for their local post office when it opened in 1802. Islip was originally a farming community, gradually transforming into a posh enclave for wealthy families in the 19th and 20th centuries. Many of the Colonial Revival, Greek Revival, Romanesque Revival, Federal, Moorish and Victorian mansions that once lined the streets of Islip have been razed, though some remain, adjacent to many newer, large homes. Islip has a wealth of extant Queen Anne Revival homes.

In 1844, the Long Island Railroad came to Islip Town and in 1865, the South Side Railroad was constructed to serve the hamlets on the bay and the area flourished.

Located along the picturesque Great South Bay, Islip has a long history associated with fishing, clamming (the world-famous Doxsee Clam Company started in Islip), swimming and boating. Islip Hamlet has its own public bathing beach, under the jurisdiction of the town. Boating and yachting are as popular today as they were years ago, if not more so, with the development of the communities on the adjacent barrier beach of Fire Island.

In 1925, the federal government erected the first Fire Island Lighthouse. On a good summer weekend, the Surf Hotel attracted 500 to 1,000 guests who came from New York and the mainland by excursion boats, ferries and chartered sloops. There was a flurry of building after World War I, but nothing like the population explosion and land development that followed World WarII. Islip’s population exploded from 71,000 in 1950 to 278,000 in 1970. Today more than 300,000 residents live, work and play in this amazing setting.