The Commonwealth of Pennsylvania is divided into seven distinct geographic numbering plan areas in the North American Numbering Plan, and served by a total of fifteen area codes. All NPAs have at least two area codes, but the large metro area of Philadelphia has three, as well as the large region surrounding it in the southeast of the state.
In 1947, the American Telephone and Telegraph Company divided Pennsylvania into four numbering plan areas and assigned one distinct area code to each. Since 1995, several relief actions in form of area code splits and overlays have expanded the number of area codes. As a result, all numbering plan areas are overlay complexes and ten-digit dialing is mandatory statewide.
| Area code | Year created | Parent NPA | Overlay | Numbering plan area |
|---|---|---|---|---|
| 215 | 1947 | – | 215/267/445 | Philadelphia and its immediately surrounding areas in the southeast corner of Pennsylvania |
| 267 | 1997 | 215 | ||
| 445 | 2018 | 215/267 | ||
| 610 | 1994 | 215 | 484/610/835 | Southeastern Pennsylvania outside Philadelphia, including the Lehigh Valley, but excluding all but northernmost Bucks County and the eastern half of Montgomery County |
| 484 | 1999 | 610 | ||
| 835 | 2022 | 610/484 | ||
| 412 | 1947 | – | 412/878 | Pittsburgh and its immediately surrounding areas in Allegheny County |
| 724 | 1998 | 412 | 724/878 | Western Pennsylvania, surrounding 412 |
| 878 | 2001 | 412 | 412/878 | Western Pennsylvania, NPA 412 and 724 |
| 724 | 724/878 | |||
| 717 | 1947 | – | 223/717 | South Central Pennsylvania, including Harrisburg, Lancaster, and York. |
| 223 | 2017 | 717 | ||
| 570 | 1998 | 717 | 272/570 | Northeastern Pennsylvania, including Scranton and Wilkes-Barre |
| 272 | 2013 | 570 | ||
| 814 | 1947 | – | 582/814 | Northwestern and central Pennsylvania, from Bedford County to Centre County, including the city of Erie |
| 582 | 2020 | 814 | ||