Area code 559 is a telephone area code in the North American Numbering Plan for the central San Joaquin Valley in central California. The numbering plan area includes the counties of Fresno, Madera, Kings, and Tulare, an area largely coextensive with the Fresno and Visalia-Porterville metropolitan areas. The area code was placed in service in 1998, when its services area was split from that of area code 209.
In 1997, the California-Nevada Code Administration (CNCA) determined that telephone number demand in the area exceeded normal forecasts, and placed area codes 209, 213, 310, 408, 619, 805, and 818 in jeopardy status of exhausting central office codes before normal relief could be implemented, triggering special conservation measures.[1]
As a result, area code 559 was created in an area code split of the 209 numbering plan area on November 14, 1998.[2] The new area code was assigned to the southern part of 209. A permissive dialing period was maintained until May 15, 1999. Although this provided general relief, the California-Nevada Code Administration (CNCA) indicated that area code 209 remained in jeopardy status for further relief actions.[2]
Like many other regions that had experienced area code changes and additions during the first boom of wireless devices, such as cellular telephones and pagers in the 1990s, both 559 and 209 were in the early planning stages of relief, potentially creating the need for introduction of further new area codes. Yet by 2002, telephone number pooling was enforced for the 209 and 559 central offices, reducing the size of telephone number blocks allocated to carriers from 10,000 to 1,000 numbers.
Area code 559 is expected to exhaust in 2025. For relief, an overlay complex with area code 357 is planned which will necessitate the implementation of ten-digit dialing (1+10-digit for landlines) in the central San Joaquin Valley.[3]
The area code serves the Central California counties of Fresno, Madera, Kings, and Tulare.
The major cities within the service region are Fresno, Coalinga, Clovis, Madera, Sanger, Reedley, Dinuba, Selma, Tulare, Visalia, Hanford, Lemoore, Porterville, Avenal, and Kingsburg.