Originally, the plan area covered the far northern portion of the state. In 1950, as part of a realignment of California's area codes, 916 was rotated to cover the northeastern corner of California, from the Sierra Nevada to the Central Valley. This involved changing Sacramento from area code 415 to 916.[citation needed]
The numbering plan area was split in a flash-cut on March 1, 1959, when area code 707 was created out of the northwest portion. On November 1, 1997, it was split again. The northeastern portion, including Redding, Yreka and Mount Shasta, became area code 530, reducing the 916 numbering plan area to Sacramento and its immediate area. On the same day, Dixon was reassigned from 916 to 707. This split left 916 as the only one of the original 86 area codes that no longer covers any part of its original area.[1]
In 2017, the CPUC approved an overlay area code to take effect in 2018, as all available prefixes were expected to be allocated by December 2018.[2] On February 9, 2017, the CPUC announced that the new overlay area code would be area code 279.[3] The new area code began service on March 10, 2018.[4]