Westchester County is a county in the U.S. state of New York. Westchester covers an area of 450 square miles (1,200 km2), consisting of 48 municipalities. According to the 2010 Census, the county had a population of 949,113, estimated to have increased by 2.5% to 972,634 by 2014. Established in 1683, Westchester was named after the city of Chester, England. The county seat of Westchester is the city of White Plains.