Tri-State area

There are a number of areas in the 48 contiguous United States known informally as tri-state areas. Often, a tri-state area is an area associated with a particular town or metropolis that lies across three states. Some, but not all, 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 climate, such as the tri-state area of Indiana, Ohio and Michigan.

The New York metropolitan area, which covers parts of the states of New York, New Jersey, and Connecticut is perhaps the most commonly identified tri-state area. It is often referenced in New York radio, as well as through countless television commercials.

The Delaware Valley region, which includes eastern Pennsylvania, southern New Jersey, and northern Delaware, is also frequently referred to as a tri-state area in radio and TV advertising in the Philadelphia market.

Four other prominent areas that have been labeled tri-state areas are the Cincinnati tri-state area, including Ohio, Kentucky, and Indiana; the Pittsburgh tri-state area, covering parts of Pennsylvania, Ohio, and West Virginia; the Chicago tri-state area, also known as Chicagoland, which includes parts of Illinois, Indiana, and Wisconsin; and the Greater Memphis area or Mid-South consisting of West Tennessee, North Mississippi, and the Arkansas delta.

...
Wikipedia