The period following the American Civil War enabled entrepreneurs in the New York area to create fortunes, and many built large estates, such as Lyndhurst, in Westchester.
During the latter half of the 19th century, Westchester's transportation system and labor force attracted a manufacturing base, particularly along the Hudson River and Nepperhan Creek.
Westchester County is one of the centrally located counties within the New York metropolitan area.
The county is positioned with New York City, Nassau and Suffolk counties on Long Island, and Long Island Sound to its south; Putnam County to its north; Fairfield County, Connecticut to its east; and Rockland County and Bergen County, New Jersey across the Hudson River to the west.
Although the Revolutionary War devastated the county, recovery after the war was rapid.
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.
In 1798, the first federal census recorded a population of 24,000 for the county.