ZIP Code 54421 — Colby, WI
54421 is a standard (street delivery) ZIP code serving Colby, Wisconsin, in Marathon County. To mail something here you only need these five digits — but the four-digit extension narrows delivery to a single point, and it is what USPS bulk postage discounts are priced on.
ZIP code 54421 at a glance
| ZIP code | 54421 |
|---|---|
| Primary city | Colby |
| State | Wisconsin (WI) |
| County | Marathon FIPS 55073 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Chicago |
| Population | 3,468 |
| Coordinates | 44.898660, -90.295320 |
How ZIP+4 works in 54421
The four digits after the hyphen encode a delivery segment inside 54421. In practice one segment usually means:
- One side of one block — odd numbers on a street between two cross streets
- A single large building, or one floor of it
- A group of PO boxes, sometimes a single box
- A single business that receives enough mail to warrant its own code
That is why 54421 has no single ZIP+4: two neighbors across the street from each other usually have different ones. Enter a street address above and we will return the exact nine-digit code along with the standardized USPS address format.
Nearby ZIP codes
Showing the closest twelve. See every ZIP code within 25 miles of 54421.
| ZIP | City | Distance |
|---|---|---|
| 54488 | Unity, WI | 4.3 mi |
| 54405 | Abbotsford, WI | 4.5 mi |
| 54425 | Dorchester, WI | 7.9 mi |
| 54422 | Curtiss, WI | 9.6 mi |
| 54479 | Spencer, WI | 9.9 mi |
| 54480 | Stetsonville, WI | 11.1 mi |
| 54460 | Owen, WI | 12.3 mi |
| 54484 | Stratford, WI | 12.6 mi |
| 54446 | Loyal, WI | 13.2 mi |
| 54426 | Edgar, WI | 15 mi |
| 54411 | Athens, WI | 16.7 mi |
| 54498 | Withee, WI | 18.4 mi |
Questions about 54421
What is the ZIP+4 code for 54421?
54421 is the five-digit ZIP code. The ZIP+4 adds four more digits that identify a specific delivery point — usually one side of a city block, a single building, or a group of PO boxes. Because those four digits change from address to address within 54421, you need to look up a specific street address to get them.
What city is 54421?
54421 is assigned to Colby, Wisconsin, in Marathon County.
Do I need to use the ZIP+4?
It is optional for ordinary mail, but it speeds up sorting and it is required for most USPS bulk-mail postage discounts. Many address-verification and e-commerce systems also use ZIP+4 to confirm a delivery point exists.
Need thousands of these?
Upload a CSV and get ZIP+4, county, carrier route, and delivery-point data appended to every row — or call the API directly.