The Southern Tier is a geographic subregion of the broader Upstate New York region of New York State, consisting of counties west of the Catskill Mountains in Delaware County and geographically situated along or very near the northern border of Pennsylvania. Definitions of the region vary widely, but generally encompass localities in counties surrounding the Binghamton and Elmira-Corning metropolitan areas. This region is bordered to the south by the Northern Tier of Pennsylvania and both these regions together are known as the Twin Tiers.