California
(628) Area Code 628 — San Francisco, California
628 Area Code – San Francisco, California: Location, Time Zone & History
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Map of Area Code 628
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History & Cultural Notes
Few area codes trace a lineage as long as the one behind 628. The story begins in 1947, when 415 was assigned as one of the original North American Numbering Plan area codes, covering a wide stretch of northern and central California. Growth steadily shrank that footprint: 408 split away in 1959 for San Jose and the South Bay, 510 followed in 1991 for the East Bay, and 650 split off in 1997 to serve San Mateo County and the Peninsula.
By the early 2010s, even the reduced 415 territory around San Francisco and Marin County was running short of central-office codes. Rather than split the region again, the California Public Utilities Commission approved 628 as an all-services overlay of 415 in December 2014, and it went into service on March 21, 2015. Ten-digit dialing became mandatory across the combined 415/628 complex from that point.
- San Francisco — financial, tourism, and technology hub
- Marin County communities including San Rafael, Sausalito, and Mill Valley
- Daly City and Brisbane along the Peninsula edge
The overlay approach let San Francisco's technology, finance, and biotechnology sectors keep their existing 415 numbers while newly assigned lines took the 628 prefix.