ZIP codes in Jefferson County
18 ZIPs touch Jefferson County, Illinois. The blue dashed line is the county border; orange ZIPs reach into it.
18
ZIP codes
11
cross the county line
59,698
people in these ZIPs
102
counties in IL
Most people
Jefferson County ZIP list
More counties in Illinois
- Hardin County6
- Henderson County17
- Henry County24
- Iroquois County28
- Jackson County23
- Jasper County15
- Jersey County11
- Jo Daviess County15
- Johnson County12
- Kane County40
- Kankakee County22
- Kendall County19
Questions people actually ask
How many ZIP codes are in Jefferson County, Illinois?
18 ZIP codes reach into Jefferson County, including 1 PO Box or single-address ZIPs placed by the town they serve. 11 of them are only partly in the county and also cover a neighboring county.
Which ZIP code in Jefferson County has the most people?
62864 (Mount Vernon) has about 22,779 residents, the most of any ZIP touching Jefferson County, in the Census Bureau’s ACS 2020–2024 estimates.
Can a ZIP code be in Jefferson 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 Jefferson 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