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ZIP codes in New Castle County

54 ZIPs touch New Castle County, Delaware. The blue dashed line is the county border; orange ZIPs reach into it.

54

ZIP codes

2

cross the county line

610,696

people in these ZIPs

3

counties in DE

Most people

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New Castle County ZIP list

More counties in Delaware

All 3 counties in Delaware

Questions people actually ask

How many ZIP codes are in New Castle County, Delaware?

54 ZIP codes reach into New Castle County, including 23 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 New Castle County has the most people?

19720 (New Castle) has about 62,392 residents, the most of any ZIP touching New Castle County, in the Census Bureau’s ACS 2020–2024 estimates.

Can a ZIP code be in New Castle 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 New Castle 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