ZIP codes in St. Clair County

16 ZIPs touch St. Clair County, Missouri. The blue dashed line is the county border; orange ZIPs reach into it.

ZIP codes

cross the county line

42,170

people in these ZIPs

115

counties in MO

Most people

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St. Clair County ZIP list

More counties in Missouri

All 115 counties in Missouri

Questions people actually ask

How many ZIP codes are in St. Clair County, Missouri?

16 ZIP codes reach into St. Clair County. 13 of them are only partly in the county and also cover a neighboring county.

Which ZIP code in St. Clair County has the most people?

65355 (Warsaw) has about 11,436 residents, the most of any ZIP touching St. Clair County, in the Census Bureau’s ACS 2020–2024 estimates.

Can a ZIP code be in St. Clair 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 St. Clair 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