Chappaqua is a hamlet and census-designated place in the town of New Castle, in northern Westchester County, New York, United States. As of the 2010 census, following a major revision to the delineation of its boundaries by the Census Bureau, the population was 1,436. At the 2000 census, with very different census-defined boundaries, Chappaqua had a population of 9,468. As of 2015, Forbes ranked Chappaqua the 317th wealthiest place in the United States with a median sale price of $1,239,747