Ulster County is a county located in the state of New York, United States. It lies in the state's Mid-Hudson Region of the Hudson Valley. In the 2010, the population was 182,493. The county seat is the city of Kingston. A part of the New York metropolitan area, the county is named for the Irish province of Ulster.
The area of present day Ulster County was called Esopus by the Dutch settlers: it was then part of the New Netherland Colony. In 1652 Thomas Chambers, a freeholder from Rensselearwyck, purchased land at Esopus and began trading there. In 1654 Johan de Hulter, owner of 20% of the Killian van Rensselaer Company was granted a patent,together with the patents of Christoffel Davids, and Jacob Jansen Stoll, this supplies evidence of the first permanent settlement, that grows into the village of Wiltwijck, later: Kingston. In 1683, the Duke of York created twelve counties in his province. Ulster County was one of them. Its boundaries at that time included the present Sullivan County, and portions of the present Delaware, Orange, and Greene Counties.
In 1777, the capital of New York State (the first state capital of independent New York) was established at Kingston, though it was subsequently moved to Kerhonkson when the British burned that city.
In 1797, portions of Otsego and Ulster Counties were split off to create Delaware County.
In 1798, the southernmost towns in Ulster County were moved into Orange County, to compensate Orange for breaking away the southernmost portion of that county in order to form Rockland County.
In 1800, portions of Albany and Ulster Counties were split off to create Greene County.
In 1809, Sullivan County was split off from Ulster County.