Area Code Atlas

NANP - SPLIT OF THE 312 NUMBERING PLAN AREA

NPA 708 split from 312

Area code 708 was created in 1989 as a geographic split from area code 312 to serve the suburbs of Chicago, Illinois, leaving 312 for the city proper.

312 NUMBERING PLAN AREA (NPA) CODE SPLIT IN ILLINOIS

NPA 708 split from 312

Area code 708 was created on November 11, 1989, in a geographic split from 312, providing a new code for the southern and western suburbs of Chicago. This split was intended to relieve exchanges in one of the largest toll-free calling zones in the nation and marked Illinois' first new area code since 309 in 1957.

NANP-Split of 312 (Illinois) Numbering Plan Area (NPA)

NPA 773 split from 312

Area code 773 was created in October 1996 as a geographic split from 312, serving the areas of Chicago outside the downtown core. The split was implemented to address number exhaustion in the original 312 territory.

NPA 773 split from 312 for outer Chicago

On October 11, 1996, area code 773 was split off from 312, with 312 retained for downtown Chicago and 773 assigned to the rest of the city. This made 312 an enclave area code.

NPA 773 split from 312 for Chicago's outer areas

Area code 773 was created on October 12, 1996, by splitting all of Chicago outside the downtown Loop area from area code 312 to accommodate growth and increased demand for numbers. The existing record already describes this split for outer Chicago, making this a duplicate with additional detail.

Permissive dialing period begins for 773 and 312

Permissive dialing began in October 1996, allowing calls within Chicago to be completed using either 312 or 773 as residents adjusted to the new area code split.

Mandatory dialing of 773 and 312 begins

Mandatory dialing of the new area code 773 began on January 11, 1997, ending the permissive dialing period where calls could be completed using the old 312 code across Chicago. The existing record already covers this event thoroughly.

Overlay planned for 312 and 773 with 872

The Illinois Commerce Commission announced on August 10, 2007, that area code 872 would overlay the existing 312 and 773 area codes in Chicago to provide additional numbering resources. The existing record already states this plan comprehensively.

NPA 872 overlay on 312 announced

NPA 872 to Overlay NPA 312 and 773 (Illinois)

NPA 872 overlay on 312 announced

NPA 872 to Overlay NPA 312 and 773 (Illinois)

NPA 872 overlay activated for 312 and 773

Area code 872 was activated on November 7, 2009, as an overlay for the 312 and 773 area codes in Chicago, Illinois, allowing for expanded numbering capacity without geographic splits. The existing record already covers this event thoroughly.

Mandatory 11-digit dialing for 312, 773, and 872

Mandatory 11-digit dialing was instituted in Chicago on November 7, 2009, coinciding with the introduction of area code 872. All local calls within the 312, 773, and 872 area codes now require dialing the full area code and number.