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(KTXL) — When telephone lines expanded across the United States, three area codes were established to cover the entire state of California. As the population grew, more area codes were introduced, but the first three are still in use.

The three original area codes, 916, 213 and 415, continue to serve regions in the southern and northern parts of the state, as well as a major metropolitan area of the coast, according to the California Public Utilities Commission. 

Area code 916

The 916 area code serves the city of Sacramento and the surrounding region, including parts of El Dorado, Solano, Sutter, Yolo, Placer, and Sacramento counties. 

In Placer County, the 916 area code serves the cities of Lincoln, Loomis, Rocklin and Roseville, according to the CPUC.

In Sacramento County, the cities that use this area code are Sacramento, Citrus Heights, Elk Grove, Folsom, Isleton, and Rancho Cordova. 

Since the 916 area code was created, it has been split twice: in 1959 (707 area code) and in 1997 (530). 

The Sacramento region does have 279 as an overlay area code after the CPUC approved it on Feb. 9, 2017. It was created to accommodate the need for additional telephone numbers in the Sacramento region. 

According to the CPUC, the overlay allows existing customers to keep their telephone numbers and the 916 area code, but any new customers or additional lines would take the new area code.

Area code 415

The 415 area code serves the San Francisco Bay Area, including the City and County of San Francisco, most of Marin County, and a small portion of San Mateo County. 

In addition to San Francisco, the 415 area code can be found in Brisbane, Daly City, Belvedere, Corte Madera, Larkspur, Mill Valley, Fairfax, Novato, Ross, San Anselmo, San Rafael, Sausalito, and Tiburon. 

When the 415 area code was created in 1947, it was split three times: in 1959 (408 area code), in 1991 (510), and in 1997 (650). 

The CPUC approved the area code of 628 on Dec. 14, 2014, to accommodate the need for more phone numbers in San Francisco Bay Area. 

Like the 916 area code, customers with the 415 area code are allowed to keep their phone numbers after the overlay approval. 

Area code 213

When the 213 area code was created, it covered the entire southern portion of California, according to a report from the CPUC. 

The 213 area code eventually split into several other codes, including 310, 323, 562, 619, 626, 714, 818, 858, 909, and 949.

The 323 area code, which is one of the main area codes in the Los Angeles region, was created in June 1998, according to the CPUC. 

“The area served by the 323 area code surrounds the region covered by the 213 area code is largely made up of the City of Los Angeles as well as neighboring cities and unincorporated portions of Los Angeles County,” the CPUC said in 2016. 

In 2016, the CPUC approved a code overlay to meet the demand that the 213 and 323 area codes can be used in the same region.