Tri-state area

There are a number of areas in the 48 contiguous United States known as tri-state areas where three states either meet at one point (a tripoint) or are in close proximity to each other. The two best known of the latter type are for the New York and Chicago metropolitan areas. Two well-known examples of the former are Philadelphia's Delaware Valley and the Pittsburgh Tri-State.

The Tri-State Region around New York City is where New York, New Jersey, and Connecticut nearly meet. There is no tripoint, however, as Connecticut does not touch New Jersey. Chicago's tri-state region includes Illinois, Indiana, and Wisconsin and is commonly referred to as Chicagoland. This tri-state region also does not have a tripoint since Indiana does not touch Wisconsin. Pittsburgh's tri-state region includes Pennsylvania, Ohio, and West Virginia, which meet near the Beginning Point of the U.S. Public Land Survey northwest of Pittsburgh. Philadelphia's tri-state area consists of Southeastern Pennsylvania, Southern New Jersey, and Delaware, with a tripoint meeting in the Delaware River near the east end of the Twelve-Mile Arc.

Other large metropolitan areas with a tri-state area include Cincinnati and Memphis. Smaller ones include those of Dubuque, Iowa, which spills over into Illinois and Wisconsin; and of Evansville, Indiana, which includes parts of Illinois and Kentucky.

The area that includes Washington, D.C. and the nearby parts of Maryland and Virginia is sometimes loosely referred to as a "tri-state area," although Washington is not a state.

The "Joplin District", a lead and zinc mining region of Oklahoma, Kansas and Missouri, produced mineral specimens known as "Tri-State" minerals.