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Area codes 610, 484, and 835 are telephoneoverlayarea codes in theNorth American Numbering Plan (NANP) for the eastern and southeastern regions ofPennsylvania. The numbering plan area (NPA) includes regions to the west ofPhiladelphia and the citiesAllentown,Bethlehem, andReading. It includes much of theDelaware Valley, including almost all ofDelaware County, most of thePhiladelphia Main Line, and all of theLehigh Valley.
Area code 610 was placed in service on January 8, 1994, in anarea code split from numbering plan area215, which had been the entire southeast quadrant ofPennsylvania since 1947.Permissive dialing of both 215 and 610 continued until the morning of January 7, 1995.[1] It was Pennsylvania's first new area code since the definition of the area code system in 1947.
Three exchanges which would have switched to 610 were instead switched to717, the area code for most of the eastern half of the state outside of the lowerDelaware andLehigh Valleys. The central office prefixes were 267 atDenver, 445 atTerre Hill, and 484 atAdamstown with 267 being renumbered as 717-336 because 717-267 was already in use atChambersburg. These exchanges were all served by independent, non-Bell telephone companies, which sought to consolidate their eastern Pennsylvania customers into one area code and would have had to change area codes regardless.
This was intended as a long-term solution, but further growth in the region over the subsequent five years, and the proliferation of cell phones and pagers, spurred the introduction of area code 484 as an overlay for the 610 region on June 5, 1999, along with the introduction of mandatoryten-digit dialing.[2]
In May 2000, area code 835 was established by thePennsylvania Public Utility Commission as an additional code for the 610/484 overlay and was intended to be implemented in 2001. However, newly developed, more efficientnumber pooling measures were introduced instead, eliminating the immediate need for the new area code. The Commission formally withdrew plans for the new code on June 23, 2005, although the code remained reserved for later use within Pennsylvania if necessary.[3] Area code 835 was eventually approved by the Public Utility Commission on December 2, 2021. Assignment of central office codes in the new area code began on September 2, 2022.[4]
In 1962,AT&T assigned NPA 610 for conversion to dial service of the Teletypewriter Exchange Service in Canada.[5][6] While Telex II use of area codes was terminated in 1981 in the U.S. byWestern Union, Canadian use of 610 continued until October 31, 1993, when it was exchanged in aflash cut forarea code 600 for non-geographic applications.[7]
The following counties andmunicipalities are in the numbering plan area:
| North:570/272 | ||
| West:717/223 | 484/610/835 | East:215/267/445,856,609/640,908 |
| South:302,410/443/667,856 | ||
| Delaware area codes:302 | ||
| Maryland area codes:301/240/227,410/443/667 | ||
| New Jersey area codes:201/551,609/640,732/848,856,908,973/862 | ||
40°05′10″N75°21′25″W / 40.086°N 75.357°W /40.086; -75.357