Area Code Atlas

NANP- Overlay of 415 Numbering Plan Area (NPA) with 628 NPA - California

NPA 628 overlay on 415 announced

NPA 628 to Overlay NPA 415 (California)

Area code 628 overlaid on 415 in 2015

Area code 628 was added as an overlay to the 415 numbering plan area on February 21, 2015, to address the exhaustion of available central office prefixes. The overlay required ten-digit dialing for all calls within the region, covering San Francisco, Marin County, and northeast San Mateo County, California.

Mandatory ten-digit dialing implemented for 415/628 overlay

Ten-digit dialing became mandatory in the 415 and 628 area codes on February 21, 2015, following the introduction of the 628 overlay to ensure sufficient numbering resources.

Overlay planned for 415 with new code 628

Area code 628 was assigned in 2015 to overlay the 415 numbering plan area to mitigate central office prefix exhaustion. This change required ten-digit dialing with prefix 1 from landlines.