Western New York is the westernmost region of the state of New York. It includes the cities of Buffalo, Rochester, Niagara Falls, Jamestown and the surrounding suburbs, as well as the outlying rural areas of the Great Lakes lowlands and Niagara Frontier, the Genesee Valley, and Chautauqua-Alleghany (or the western Southern Tier.) The historic beginnings of the region can be defined by its original eastern boundary of Preemption Line, created by the December 16, 1786 political settlement between the states of New York and Massachusetts, both of which claimed political dominion over the land. This eastern boundary shifted because of changing county borders in the late 18th and early 19th centuries.