Mount Sinai is a hamlet and census-designated place (CDP) located within the Town of Brookhaven in Suffolk County, New York, United States. The population was 12,118 at the 2010 census. The hamlet is located on the North Shore of Long Island, and is served by the Mount Sinai School District. Mount Sinai's ZIP code is 11766.
Mount Sinai was first settled in the 1660s and was known by the name of Old Mans until a name change in the 1840s. Initially an agricultural hamlet, it transitioned into a popular resort town in the late-19th century and developed into a suburb of New York City in the mid-20th century. While primarily a residential community, the hamlet contains Mount Sinai Harbor and its popular public beach, Cedar Beach.
The area now known as Mount Sinai was originally called Nonowatuck, or "stream that dries up", by the Seatocot family of native Americans who lived here. The first European settlers were Colonial settlers living in what is now Setauket, who obtained a deed from these local Native Americans in 1664.
During the American Revolution, the area and Old Mans Harbor were under British control. However, because of its remote location the British did not have troops stationed here. Many citizens moved their families to Connecticut during British occupation. During the course of the war, American agents visited local patriots and received information, clothing, supplies and money to support the cause. In 1780, American Major Benjamin Tallmadge and a detachment of Continental Army dragoons landed at Cedar Beach and traveled south to successfully attack the British at Manor St. George. The route he and his men took is now marked as a historic trail.
Development as agricultural hamlet
Building of houses occurred in spurts. Initially most building occurred within a mile (2 km) of the harbor. Few houses were built south of North Country Road until the late 19th century. Much of the land south of North Country Road was owned and cultivated by farmers.
There is no known 17th-century structure still standing. The 18th century is represented by six buildings dating from 1705 to 1790. Certain of these homes have structural elements which date from the early period. The 19th century has the largest number of surviving historical structures. These can be divided into two periods, 1800-1840s and 1880-1890s. Again, some of these buildings incorporated structural elements of earlier periods.
In 1840 the people of Old Mans applied for a post office. Evidently Old Mans was not considered a proper name for the area. The name was changed to Mount Vernon. This name was used for only a year as there already was a Mount Vernon in New York. Old Mans was used once again, but for unknown reason another name change occurred.The name Mount Sinai, after the biblical mountain, was chosen by the first postmaster, Charles Phillips. Local legend says that he chose the name arbitrarily by pointing a needle at random into his Bible. Mount Sinai is the name residents have used since 1841/1842.
In addition to the farmland that populated Old Mans, the town's trees provided much of the wood for the shipbuilding trade centered in neighboring Port Jefferson. A shipyard existed in Old Mans for a time, but this was moved to the naturally deeper harbor of Port Jefferson. Riggers, sail-makers, ship carpenters and others lived in Mount Sinai and commuted to Port Jefferson. Grist mills were located somewhere along Pipe Stave Hollow and Crystal Brook Hollow roads. Records indicate that a number of windmills were located on the hills overlooking the harbor.
As the population expanded, a number of businesses were established along Route 25A. A commercial center did not develop in Mount Sinai and residents depended on businesses in the neighboring village of Port Jefferson.
Once the Long Island Railroad reached adjacent Port Jefferson in 1879, and temporarily continued into Mount Sinai from 1895-1939, new visitors and residents began appearing from New York City and from elsewhere on Long Island in order to enjoy the hamlet's beaches and bucolic setting.
The development of Mount Sinai for its natural and recreational qualities had begun with the 1841 establishment of a special care facility for sick and disabled children on the southwestern side of Mount Sinai Harbor. This consisted of housing and volunteer workers on a plot, with the location being chosen due to its close proximity to St. Charles Hospital in adjacent Port Jefferson. On April 2, 1892, this parcel was sold to Dr. Jerome Walker, who established the Crystal Brook Park Association which is still owned and occupied today by Mount Sinai's oldest private community known as Crystal Brook Park.
Seasonal vacation houses were erected along Mount Sinai Harbor. Cedar Beach, which is located on a peninsula that divides the harbor from the Long Island Sound, became a popular recreational destination. The Chandler Estate, on Mount Sinai Harbor's southern side, was repurposed as vacation cottages and housed Marilyn Monroe and Arthur Miller during their holidays in the 1950s.
In the first half of the 20th century the pace of building slowed. Although large tracts of farmland persisted, there were small pockets of development around the hamlet. Examples of these are the "colony" of homes built off Pipe Stave Hollow Road, both north and south of Route 25A, and the scattered development on Mt. Sinai and Chestnut avenues. During this time a community was mapped but never developed just south of Route 25A and east of Crystal Brook Hollow Road.
It was not until the 1960s that housing developments began to occur as suburbanization spread eastward. Lands once farmed were now sold and developed into homes for new residents of Mount Sinai. This included the sale and development of the 404-acre Davis Peach Farm in the first years of the 2000s.
Recently, many private communities have been built in Mount Sinai. These communities include Pulte Villages, Island Estates, The Hamlet at Willow Creek, and The Ranches at Mt. Sinai. This rapid growth has replaced much of the farmlands at an astounding rate for the past 5–10 years, and almost none is now left.