Ulster County is a county located in the state of New York. Ulster County sits in New York state’s Mid-Hudson Region of the Hudson Valley. As of the 2000 census, the population of Ulster County is 177,749. It is the northernmost county and largest county (by land area) in the New York Metropolitan Area. The county seat and only large city is Kingston. Ulster County is named for the Irish province of Ulster, then an earldom of the Duke of York (later James II).