Westchester County is a county in New York State, at the northern border of New York City. A million people live there. It acts as a suburb of New York, with many of its residents commuting to jobs there. The largest city is Yonkers, and other important cities include White Plains and New Rochelle. The County shares borders with Putnam County to the north, and Fairfield County, Connecticut to the East. The Hudson River is on the west.