Tri-state area

Tri-state area is an informal term in the United States which can be used for any of several populated areas associated with a particular town or metropolis that, with adjacent suburbs, lies across three states. Some of these involve a state boundary tripoint. Other tri-state areas have a more diffuse population that shares a connected economy and geography—especially with respect to geology, botany, or climate. The term "tri-state area" originated as a term to describe the New York City metro area, and can be heard in radio, television commercials and some movies..

Source: Wikipedia