In 1947, when the
American Telephone and Telegraph Company (AT&T) devised the first nationwide
telephone numbering plan and assigned the
original North American area codes, the state of California was divided into three numbering plan areas: 213,
415, and
916, for the southern, central, and northern parts of the state, respectively. The area served by 213 extended from the
Mexican border to the
Central Coast. Starting in the 1950s, Southern California experienced rapid expansion of telephone service, requiring area code 213 to be split five times by 1998. The first split became necessary in 1951, when most of the southern and eastern portion, including
San Diego and most of
Orange County, was assigned
area code 714. The 714 numbering plan area was further divided on November 14, 1992, when
area code 909 was assigned to the majority of Riverside, San Bernardino, Ontario, and Pomona. On July 17, 2004, numbering plan area 909 was divided in a two-way geographic split for assignment of area code 951 to the southern portion of 909. The new numbering plan area comprised western
Riverside County, including the cities and communities of
Banning,
Beaumont,
Corona,
Canyon Lake,
Riverside,
Temescal Valley,
Woodcrest,
Moreno Valley,
Perris,
Menifee,
Lake Elsinore,
Wildomar,
Murrieta,
Temecula,
San Jacinto,
Hemet,
Lakeview,
Nuevo,
Norco,
Eastvale,
Jurupa Valley, and
Idyllwild. The creation of area code 951 is the latest area code split in California. All codes introduced in the state since have been overlays. Prior to October 2021, area code 951 had telephone numbers assigned for the
central office code 988. In 2020,
988 was designated nationwide as a dialing code for the
National Suicide Prevention Lifeline, which created a conflict for exchanges that permit
seven-digit dialing. This area code was therefore scheduled to transition to
ten-digit dialing by October 24, 2021. ==Service area==