Area codes 610 and 484
Area codes 610 and 484 are telephone area codes in the North American Numbering Plan (NANP) for the eastern and southeastern regions of the U.S. state of Pennsylvania. The numbering plan area (NPA) includes regions to the west of Philadelphia, along with the cities Allentown, Bethlehem, and Reading. It includes much of the Delaware Valley, including almost all of Delaware County and most of the Philadelphia Main Line. Area code 835 is scheduled to be added as an additional area code for the overlay plan in 2022. History. Area code 610 was created on January  8, 1994 as a split from numbering plan area 215, which had been the entire southeast quadrant of Pennsylvania since 1947. Permissive dialing of both 215 and 610 continued until the morning of January 7, 1995. It was Pennsylvania's first new area code since the implementation of the area code system in 1947. Three exchanges which would have switched to 610 were instead switched to 717, the area code for most of the eastern half of the state outside of the lower Delaware and Lehigh Valleys. They were 267 at Denver, 445 at Terre Hill, and 484 at Adamstown , with 267 being replaced with 717-336 because 717-267 was already in use at Chambersburg. These exchanges were all served by non-Bell telephone companies which sought to consolidate their eastern Pennsylvania customers into one area code, and would have had to change area codes anyway. 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 mandatory ten-digit  dialing. Area code 835 was intended as an additional overlay code for the 610 and 484 numbering plan area, as announced by the Pennsylvania Public Utility Commission in May 2000 and to be implemented in 2001. However, newly developed, more efficient number 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 remains reserved for later use within the Commonwealth if necessary. Under the most recent projections, the region will need another area code by the summer of 2024. Area  code 835 was finally approved by the Public Utility Commission in a unanimous vote on December 2, 2021. Numbers in the new 835 Area Code will become available for assignment on September 20, 2022. Area code 610 was the last area code assigned with the digit "1" in its middle position. When area codes were introduced in 1947, all numbers followed the pattern N0X or N1X (where the middle digit was either a zero or one). By 1994, area code 610 was the last remaining number in this group. The next new area codes after 610 to be assigned (334  in Alabama and 360 in Washington, both in 1995) were the first to break this rule. The numbering plan area comprises the following counties: The following towns and cities are included in the numbering plan area: Allentown, Bethlehem, Catasauqua, Chadds Ford, Chester, Christiana, Downingtown, Easton, Emmaus, Exton, Folsom, Gap, Hamburg, Havertown, Kutztown, Lehighton, Macungie, Malvern, Media, Newtown Square, North Catasauqua, Northampton, Oxford, Palmerton, Paoli, Pottstown, Reading, Shillington, Sinking Spring, Tamaqua, Upper Darby, West Chester, Whitehall Township, Willistown, Wind Gap, Wyomissing. Prior usage for TWX. Most of the N10 area codes (510, 710, 810, and 910) were used prior to 1981  by AT&T for their TWX, or Teletypewriter Exchange Service (TWX) network. Telex use of these area codes in the United States was decommissioned in 1981 when Western Union, who had acquired the TWX network in 1969 from AT&T, and renamed it Telex II, upgraded the network to "4-row" ASCII operation. Area code 510 was reassigned to Oakland, California in 1991, 710 went to the US federal government in 1983, 810 and 910 were assigned to Michigan and North Carolina, respectively in 1993. The last TWX code, 610, outlived the others because it was controlled by Bell Canada, and not  directly affected by AT&T's exit from teletype services. Area code 610 was replaced with non-geographic Canadian area code 600 in 1992, freeing the area code for reassignment to general telecommunication services. When it was reassigned in 1994, area code 610 was the last geographic area code assigned to follow the original pattern of having the digits "1" or "0" in the middle position. In 1995, the assignment of interchangeable NPA codes commenced, which broke the pattern.