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ZIP codes in Hamilton County

15 ZIPs touch Hamilton County, Iowa. The blue dashed line is the county border; orange ZIPs reach into it.

15

ZIP codes

10

cross the county line

38,730

people in these ZIPs

99

counties in IA

Most people

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Hamilton County ZIP list

More counties in Iowa

All 99 counties in Iowa

Questions people actually ask

How many ZIP codes are in Hamilton County, Iowa?

15 ZIP codes reach into Hamilton County. 10 of them are only partly in the county and also cover a neighboring county.

Which ZIP code in Hamilton County has the most people?

50036 (Boone) has about 16,154 residents, the most of any ZIP touching Hamilton County, in the Census Bureau’s ACS 2020–2024 estimates.

Can a ZIP code be in Hamilton 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 Hamilton 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