What is what area code is 618?

Area code 618 is a telephone area code in the North American Numbering Plan (NANP) for the state of Illinois in the United States. It covers the southern part of the state, including cities such as Belleville, Carbondale, Collinsville, Edwardsville, and Granite City. Area code 618 was first put into service on January 3, 1989, as a split from area code 217. It currently serves the southwestern and southern parts of Illinois.