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County ZIP codes · Kentucky · FIPS 21003

Allen County, KY ZIP Codes

Allen County, Kentucky has 6 ZIP codes (Census 2020 ZCTA-county file; GeoNames postal codes, October 2026), all residential. 3 of the residential ones lie mainly in Allen County and 3 mainly in a neighboring county; 3 cross the county line. Median household income ranges from $59,113 in 42134 (Franklin) to $113,705 in 42122 (Alvaton) (Census Bureau, ACS 2020-2024).

  • ACS2020-24
  • Census2020

Where are the ZIP codes of Allen County?

42120 · Adolphus: $65k42122 · Alvaton: $114k42133 · Fountain Run: $62k42134 · Franklin: $59k42153 · Holland: –42164 · Scottsville: $60k42164421344213342122421204215342120 · Adolphus: $65k42122 · Alvaton: $114k42133 · Fountain Run: $62k42134 · Franklin: $59k42153 · Holland: –42164 · Scottsville: $60k421644213442133421224212042120 · Adolphus: $65k42122 · Alvaton: $114k42133 · Fountain Run: $62k42134 · Franklin: $59k42153 · Holland: –42164 · Scottsville: $60k4216442134421334212242120
The residential ZIP codes of Allen County (whole outlines, including the parts in neighboring counties), shaded by median household income in national fifths (ACS 2020-2024). <$54.1k$98.1k+no figure

Source: U.S. Census Bureau, 2020 ZCTA cartographic boundaries; ACS 2020-2024 5-year estimates (B19013).

How different are its ZIP codes?

The middle half of its ranked ZIP codes (1,000+ people living in households) report median household incomes between $60,106 and $64,958.

They carry 6 postal town names: Franklin, Scottsville, Alvaton, Adolphus, Fountain Run, Holland.

Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates (B19013).

All 6 residential ZIP codes in Allen County

3 ZIP codes lie mainly in Allen County; 3 more reach into it from a neighboring county and follow the first table.

Residential ZIP codes mainly in Allen County, largest first; "In this county" is the share of the ZIP's land in the county
In this county
42164 Scottsville 17,673 68 $60k $197k 100%
42120 Adolphus 2,745 63 $65k $179k 100%
42153 Holland 18 4 – – 100%

Partly in Allen County

Residential ZIP codes mainly in another county that reach at least 1% into Allen County, by their share here
In this county
42133 Fountain Run 1,456 19 $62k $164k 24%
42134 Franklin 19,380 91 $59k $227k 7%
42122 Alvaton 5,513 146 $114k $297k 5%

Download the 6 ZIP codes as CSV

Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates; county shares by land area (Census 2020 ZCTA-county relationship file).

Which ZIP codes cross the county line?

3 ZIP codes of Allen County extend into another county. A ZIP code follows mail routes, not county borders.

Share of each ZIP code's land in Allen County and in the neighboring counties
ZIPIn AllenElsewhere
421347%Simpson County 93%
421225%Warren County 95%
4213324%Monroe County 43%; Barren County 32%

Source: U.S. Census Bureau, 2020 ZCTA-county relationship file (shares of land area).

Which first three digits do Allen County's ZIP codes use?

The first three digits of a ZIP code name the sectional center, the mail processing plant that sorts it. Every ZIP code of Allen County starts with 421.

Three-digit prefixes of Allen County's ZIP codes, the sectional center for each (USPS labeling list L005, effective October 1, 2026) and how many of the prefix's codes are Allen County's
PrefixSectional centerHereAll codes
421 Nashville, TN (SCF 370) 6 33

Source: U.S. Postal Service, labeling list L005 (3-digit ZIP Code prefix groups, SCF sortation), effective October 1, 2026.