In 1898, the Long Island Railroad arrived, bringing with it wealthy New Yorkers looking for country homes with easy transportation to more urban areas of New York City. The Manhasset name was adopted in 1840 and comes from the native word 'Manhanset', roughly meaning 'the island neighborhood.' Dairy farming was still a major endeavor, but the oyster industry was also on the rise. In 1801, it cost two cents to travel between Roslyn and Spinney Hill on the North Hempstead Turnpike, the newly opened toll road (now Northern Boulevard).

The Northern communities and villages, dominated by Yankee Congregationalists supported independence. The Town of North Hempstead separated from the Town of Hempstead in 1784 because the South, inhabited mainly by Church of England people, was loyal to the king. Many structures and properties, such as the 1719 Quaker Meeting House were burned, seized or damaged. ĭuring the American Revolution, Little Cow Neck suffered at the hands of the British. Manhasset took on the name Little Cow Neck, Port Washington was known as Upper Cow Neck. The area was more formally divided among the settlers when the fence was removed in 1677. The settlers came to an agreement that each of them could have one cow on the neck for each section of fence the individual had constructed. By 1659, there were over 300 cows and 5 mi (8 km) fence separating Cow Neck from the areas to the south. Cow Neck was so called because it offered good grazing land. Manhasset Bay was previously known as Schout's Bay (a schout being roughly the Dutch equivalent of a sheriff), Martin Garretson's Bay (Martin Garretson was the Schout at one point), and later Cow Bay or Cow Harbor. A 1643 land purchase made it possible for English settlers to return to Cow Neck (the peninsula where present-day Port Washington, Manhasset, and surrounding villages are located.).

In 1623, the area was claimed by the Dutch West India Company and they began forcing English settlers to leave in 1640. These Native Americans called the area Sint Sink, meaning 'place of small stones'. The Matinecock had a village on Manhasset Bay. Manhasset Valley Park, formerly a minor harbor

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