Area codes 573 and 235

When the American Telephone and Telegraph Company (AT&T) created a universal North American telephone numbering plan for Operator Toll Dialing in 1947, Missouri was divided into two numbering plan areas (NPAs), which received the area codes 314 and 816.

The largest city of the area code was St. Louis on the Mississippi river in the east.

By 1995, the telephone subscriber base had experienced substantial growth, threatening the exhaustion of the numbering pool.

On May 1, 2022, the Missouri Public Service Commission (MPSC) approved an all-services distributed overlay complex for the 573 numbering plan area, effective March 24, 2024.

On June 17, 2022, the NANP Administrator assigned area code 235 for the relief action, beginning with a permissive dialing period of six months on August 26, 2023 (as 573 was not affected by the 2021 requirement to change to ten-digit dialing due to the implementation of the 988 Suicide & Crisis Lifeline).