40121 ZIP Code: Fort Knox, Kentucky
ZIP code 40121 covers Fort Knox, Kentucky. It sits in Hardin County. Fort Knox is covered by 2 ZIP codes in total, so 40121 is one delivery area within it rather than the whole city. A ZIP code is a US Postal Service mail route, not a boundary on a map, so it describes where post is delivered rather than an administrative area.
| ZIP code | 40121 |
|---|---|
| Place | Fort Knox |
| State | Kentucky (KY) |
| County or equivalent | Hardin County |
| ZIP codes covering Fort Knox | 2 |
| Phone area codes in Kentucky | 5 |
| Country | United States |
Other ZIP codes in Fort Knox
ZIP codes near 40121
- 40122 Fort Knoxabout 1 mile
- 40155 Muldraughabout 4 miles
- 40175 Vine Groveabout 4 miles
- 40160 Radcliffabout 5 miles
- 40177 West Pointabout 7 miles
- 40162 Rineyvilleabout 10 miles
- 40108 Brandenburgabout 10 miles
- 40117 Ekronabout 11 miles
Distances are straight-line, between the approximate centres of each delivery area.
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Frequently asked questions
Where is ZIP code 40121?
ZIP code 40121 is in Fort Knox, Kentucky, in Hardin County. ZIP codes are mail delivery routes rather than mapped regions, so the code identifies a set of addresses the Postal Service serves together, not a district with fixed borders.
What county is 40121 in?
40121 is in Hardin County, Kentucky. A single ZIP code can straddle a county line, because mail routes were drawn for delivery efficiency and take no notice of county boundaries, so the county shown is the one the code is primarily associated with.
What area code goes with ZIP code 40121?
ZIP codes and telephone area codes are separate systems with different boundaries, so no ZIP code maps to exactly one area code. Kentucky uses 5 geographic area codes: 270, 364, 502, 606 and 859.
How many ZIP codes does Fort Knox have?
Fort Knox, Kentucky has 2 ZIP codes in this dataset, of which 40121 is one. Large cities are split across many codes so mail can be sorted by district, and the codes are usually numerically close to each other.
Is 40121 a real ZIP code?
Yes. 40121 appears in the GeoNames postal-code dataset as an active US code assigned to Fort Knox, Kentucky. Codes that have been retired or never issued do not appear, which is why entering one on this site returns a not-found page rather than a blank record.
Why do ZIP code boundaries look odd on maps?
Because they are not boundaries. A ZIP code is a collection of mail routes, and a route is a line a carrier walks or drives, not an area. Any ZIP code map you have seen is somebody's approximation drawn around the addresses in a code, which is also why two ZIP code maps rarely agree with each other.
Can two addresses in the same ZIP code be in different cities?
Yes, routinely. The Postal Service assigns a preferred city name to each code for addressing purposes, and that name often covers several neighbouring towns, unincorporated areas or a whole postal district. The place shown here is the one the source names for the code, not a claim that every address in it is inside that town's limits.
ZIP code, place, county and location data from GeoNames, used under CC BY 4.0, extracted 2026-08-22. ZIP codes are Postal Service delivery routes, not administrative areas, so a code can cross city and county lines and the place name shown is the one the source records for the code. Coordinates are an approximate centre of the delivery area, not a precise location. Population and time zone are not shown because the source does not publish them.