The telephonic area codes which are there in the city of Illinois is the NANPA area code covering the boundaries of Central Illinois, including the capital city of Springfield as well as the cities of Champaign, Urbana, Decatur, Danville, Quincy, and Rantoul.

NANP is the abbreviation of North American Numbering Plan and forms an integral part being the telephone numbering plan of 24 countries and territories. In these countries and territories includes United States and its immediate neighbours like Canada, Bermuda and 16 other Caribbean countries. NANP is also used by synechdoche, to refer to the geographic area in which that plan has been implemented.

To describe more, NANP is a system of NPA with 3-digit and 7-digit numbers that transfers the calls from one area to another using public switched telephone number or PSTN. The wires are routed using local network.

This particular area code was formed back in some years before. After that it went through a lot of splits and in the present time it is only the borough of Illinois which retains this particular area code. The towns, districts and other important areas which are around this particular area code are as follows:

Big Spring Township, Chambersburg, Clarksburg Township, Cold Spring Township, Dry Point Township, Effingham, Fishhook, Flat Branch Township, Greenup, Herrick Township, Holland Township, Jacksonville, Lincoln, Macon, Meredosia, Monticello, Moweaqua Township, Okaw Township, Pana, Penn Township, Pickaway Township, Riverton, Rockport, Seehorn, Summer Hill, Thawville, Toledo, Tolono, Tuscola, Virden and White Heath.