Area Code Atlas

Area code 412 created as original NPA for southwestern Pennsylvania

In 1947, area code 412 was created as one of the original North American area codes. It was assigned to the entire southwestern corner of Pennsylvania, including Pittsburgh and surrounding areas.

NANP-Overlay of 412 (Pennsylvania) Numbering Plan Area (NPA)

Important Notice of Delay in Implementation of NPA Relief for the 412 NPA (Pennsylvania)

Extraordinary NPA-Specific Conservation Procedures for 215 and 412 NPAs (Pennsylvania)

NANP-Split of 412 (Pennsylvania) Numbering Plan Area (NPA)

NPA 724 split from 412

Area code 724 was created in 1998 as a geographic split from 412, taking over most of the territory outside of Pittsburgh. The split was chosen over an overlay due to resistance to ten-digit dialing at the time.

NPA 724 split from 412

On February 1, 1998, area code 724 was created from a split of 412, assigning nearly all of the 412 territory outside Allegheny County to the new code. This change made 412 an enclave for the city of Pittsburgh, while 724 served the surrounding suburbs and southwestern Pennsylvania.

Extraordinary NPA-Specific Jeopardy Conservation Procedures Announced for 412 NPA (Pennsylvannia)

NPA 878 to Overlay NPAs 412 and 724 (Pennsylvania)

Permissive 10-digit dialing begins for 412 and 724

Permissive 10-digit dialing began on July 17, 2000, for calls within and between the 412 and 724 area codes in preparation for the 878 overlay. Callers could use either seven or ten digits during this transition period.

Ten-digit dialing becomes mandatory in southwestern Pennsylvania

In 2001, ten-digit dialing became mandatory across southwestern Pennsylvania due to the implementation of the 878 overlay for both 412 and 724. This change affected all customers in the region.

Rationing in NPAs 412, 724, and 878 (Pennsylvania)

Mandatory 10-digit dialing for 412 and 724

Mandatory 10-digit dialing was implemented on July 12, 2001, for all calls within and between the 412 and 724 area codes, coinciding with the overlay of area code 878. Seven-digit dialing was discontinued.

Area code 878 overlays 412

On August 17, 2001, area code 878 was implemented as an overlay for area code 412. This change was made to provide additional numbering resources for the Pittsburgh region.

NPA 878 overlay implemented for 412 and 724

Area code 878 was activated on August 17, 2001, as an all-services overlay for both 412 and 724 in southwestern Pennsylvania. This overlay required mandatory ten-digit dialing throughout the region and was implemented after both 412 and 724 faced number exhaustion.

Mandatory ten-digit dialing begins in 412, 724, and 878 simultaneously

Ten-digit dialing became mandatory in the 412, 724, and 878 numbering plan areas on August 17, 2001, coinciding with the activation of the 878 overlay to accommodate growing demand for telephone numbers in southwestern Pennsylvania.

First telephone numbers assigned for area code 878 in 412 region

In 2013, telephone numbers were first assigned for area code 878 in the 412 region, more than a decade after the overlay was implemented.

First 878 central office prefix assigned in 412 territory

The first central office prefix (999) using area code 878 was assigned in the 412 territory on September 15, 2015, marking the beginning of 878 number assignments in the Pittsburgh area.

First 878 central office prefix assigned in 412 territory

The first 878 central office prefix (999) was assigned in the 412 territory on September 15, 2015, marking the start of 878 number assignments in Pittsburgh.