ZIP Code 51231 — Archer, IA
51231 is a standard (street delivery) ZIP code serving Archer, Iowa, in O'Brien 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 51231 at a glance
| ZIP code | 51231 |
|---|---|
| Primary city | Archer |
| State | Iowa (IA) |
| County | O'Brien FIPS 19141 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Chicago |
| Population | 562 |
| Coordinates | 43.105670, -95.741310 |
How ZIP+4 works in 51231
The four digits after the hyphen encode a delivery segment inside 51231. 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 51231 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 51231.
| ZIP | City | Distance |
|---|---|---|
| 51245 | Primghar, IA | 7.3 mi |
| 51238 | Hospers, IA | 7.8 mi |
| 51248 | Sanborn, IA | 8 mi |
| 51201 | Sheldon, IA | 8.2 mi |
| 51046 | Paullina, IA | 10.1 mi |
| 51022 | Granville, IA | 10.3 mi |
| 51244 | Matlock, IA | 13.6 mi |
| 51232 | Ashton, IA | 14 mi |
| 51009 | Calumet, IA | 14.6 mi |
| 51003 | Alton, IA | 14.9 mi |
| 51346 | Hartley, IA | 15.3 mi |
| 51234 | Boyden, IA | 15.3 mi |
Questions about 51231
What is the ZIP+4 code for 51231?
51231 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 51231, you need to look up a specific street address to get them.
What city is 51231?
51231 is assigned to Archer, Iowa, in O'Brien 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.