Area codes 618 and 730

The numbering plan area (NPA) comprises one hundred and twenty-six municipalities, such as Carbondale, Cairo, Belleville, East St. Louis, Edwardsville, Marion, O'Fallon, Alton, Mt.

Vernon, Centralia, Herrin, Salem, Metropolis, Fairview Heights, Collinsville, and Granite City.

When the American Telephone and Telegraph Company (AT&T) organized the nation's telephone networks in 1947 under a new nationwide telephone numbering plan, Illinois was divided into four numbering plan areas to accommodate large number of central offices that were necessary for the state's dense population and toll call routing infrastructure.

Projections in 2021 by the North American Numbering Plan Administrator, indicated central office code exhaustion by 2025.

This area code was therefore scheduled to transition to ten-digit dialing by October 24, 2021.