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ZIP codes in San Mateo County

38 ZIPs touch San Mateo County, California. The blue dashed line is the county border; orange ZIPs reach into it.

38

ZIP codes

2

cross the county line

759,988

people in these ZIPs

58

counties in CA

Most people

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San Mateo County ZIP list

More counties in California

All 58 counties in California

Questions people actually ask

How many ZIP codes are in San Mateo County, California?

38 ZIP codes reach into San Mateo County, including 7 PO Box or single-address ZIPs placed by the town they serve. 2 of them are only partly in the county and also cover a neighboring county.

Which ZIP code in San Mateo County has the most people?

94080 (South San Francisco) has about 64,761 residents, the most of any ZIP touching San Mateo County, in the Census Bureau’s ACS 2020–2024 estimates.

Can a ZIP code be in San Mateo County and another county?

Yes. ZIP codes follow mail routes, not county lines. Rows marked with a percentage show how much of that ZIP’s land is in San Mateo County. For one address, pin the exact spot on the ZIP finder to see its county.

Where does this list come from?

ZIP areas and their county overlaps come from the Census Bureau’s 2020 ZIP Code Tabulation Area to county relationship file. PO Box ZIPs have no area, so each is placed in the county of the ZIP area nearest the town it serves.

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Updated 2026-11-10 · Where the data comes from