Dutch settlers began arriving in the 1620s, followed by settlers from England in the 1640s.
It shares its southern boundary with New York City and its northern border with Putnam County. Census Bureau, the county has a total area of 500 square miles (1,300 km), Pelham Bay Park is the largest of New York City's parks, forming a substantial buffer between suburban Westchester and the urban Bronx, while Van Cortlandt Park to the west acts as a similar buffer.
It is bordered on the west side by the Hudson River and on the east side by the Long Island Sound and Fairfield County, Connecticut. Westchester's Long Island Sound shore is generally rocky, interspersed with tidal mud flats, marshes and wetlands, as well as several natural and artificially-maintained sand beaches.
The Croton Dam and Aqueduct was begun in 1837 and completed in 1842; now a National Historic Landmark, the Croton Aqueduct is considered one of the great engineering achievements of the 19th century.
In the 1840s, the first railroads were built in Westchester, and included the New York and Harlem Railroad, the Hudson River Railroad, and the New York and New Haven Railroad.
At the time of European contact in the 16th and 17th centuries, the Native American inhabitants of present Westchester County were part of the Algonquian peoples, whose name for themselves was Lenape, meaning the people.
They called the region Lenapehoking, which consisted of the area around and between the Delaware and Hudson Rivers.During the 20th century, the rural character of Westchester would transform into the suburban county known today.The Bronx River Parkway, completed in 1925, was the first modern, multi-lane limited-access roadway in North America.The development of Westchester's parks and parkway systems supported existing communities and encouraged the establishment of new ones, transforming the development pattern for Westchester.With the need for homes expanding after World War II, multistory apartment houses appeared in the urbanized areas of the county, while the market for single-family houses continued to expand. Major interstate highways were constructed in Westchester during the 1950s and 1960s.Several different tribes occupied the area, including The Manhattans, and the Weckquaesgeek and Siwanoy bands of the Wappinger in the south, and Tankiteke, Sintsink and Kitchawank Wappinger in the north.