In the original configuration of the
first nationwide telephone numbering plan of 1947, all of New Jersey was a single numbering plan area, assigned the lowest-numbered area code,
201. In 1956, it was split to create a second numbering plan area, 609. This division generally followed the dividing line between
North Jersey, proximate to
New York City, and
South Jersey, proximate to
Philadelphia and the
Jersey Shore. Despite the division into two numbering plan areas, all calls within the state of New Jersey were dialed without area codes until July 21, 1963. Despite the presence of the Philadelphia suburbs, Trenton, Princeton and Atlantic City, South Jersey is not as densely populated as North Jersey. As a result, while North Jersey went from one area code to four during the 1990s, 609 remained the sole area code for the southern half of New Jersey for 41 years. By the late 1990s, the proliferation of cell phones and pagers, particularly in the Philadelphia suburbs, Trenton, and in Atlantic City, necessitated a new area code in South Jersey. In 1999, the southwestern part of the 609 territory, including most of the New Jersey side of the
Philadelphia area, was split off with
area code 856. The new area code entered service on June 14; permissive dialing of 609 continued across South Jersey until November 14. Since that time, the 609 territory includes parts of
Central Jersey, South Jersey and the Jersey Shore, and many parts of Burlington County. It also includes portions of southern
Middlesex County in
Plainsboro,
Cranbury, parts of
South Brunswick (particularly
Kingston) and the extreme southern part of
Monroe. The boundary was drawn so that several towns were divided between by area codes, but office code protection afforded the convenience of seven-digit dialing. about 15 months later than projected a year earlier.
Permissive dialing for all calls in 609 began on January 20, 2018, and ended August 18 when ten-digit dialing became mandatory. Overlay code 640 entered operation on September 17, 2018. With the implementation of the overlay, the New Jersey Board of Public Utilities ordered the removal of
central office code protection for a group of central offices between NPA 609 and 856, that had been in effect since the 1999 split to permit seven-digit dialing in the local area to the adjacent NPA. ==See also==