San Diego County, California, operates under a dual area code system: 619 and 858. These codes serve the vast majority of the county’s residents and businesses, a system that has evolved significantly since its inception in the mid-20th century.
The story of San Diego’s area codes begins in 1947, when the American Telephone and Telegraph Company (AT&T) first devised a nationwide telephone numbering plan. Initially, California was divided into three numbering plan areas, which were later reorganized geographically in 1950. The need for expansion first arose in 1951, leading to the assignment of area code 714 to the southern and eastern portions of the state, including San Diego and much of Orange County.
As the population grew, so did the demand for telephone numbers. In 1982, area code 714 was split, and almost all of the southernmost portion of California, stretching from San Diego to the Nevada border, received the new area code 619. This marked the first addition of a new area code in California since 1959, when 707 was introduced.
Further expansion became necessary in the late 1990s. On March 23, 1997, a portion of the 619 numbering plan area, encompassing outer northern San Diego County, desert areas, and parts of southeastern California, was removed to create area code 760. This split paved the way for even more changes.
The California Public Utilities Commission requested a more comprehensive restructuring of the 619 area code. On June 30, 1998, the North American Numbering Plan Administration (NANPA) approved a two-phase, three-way split. The first phase, implemented on June 12, 1999, introduced area code 858 to northwest San Diego County. This created an overlay system, meaning both 619 and 858 would serve the same geographic area.
The second phase of the split, originally planned for June 10, 2000, involved the creation of area code 935 for the southern and eastern parts of the county. However, the implementation of 935 did not occur as initially planned.
By 2019, the boundary between area codes 619 and 858 was eliminated altogether, solidifying the overlay complex. Today, both area codes serve the entirety of San Diego County. Area code 858 currently serves San Diego and surrounding areas, functioning as an overlay to 619, meaning both codes cover the same geographic region.
The evolution of San Diego’s area codes reflects the region’s substantial growth and the ongoing need to accommodate increasing demand for telephone numbers. The current system, with its overlay complex, aims to provide sufficient numbering resources for the foreseeable future.
