ZIP Code 52321 — Onslow, IA
52321 is a standard (street delivery) ZIP code serving Onslow, Iowa, in Jones 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 52321 at a glance
| ZIP code | 52321 |
|---|---|
| Primary city | Onslow |
| State | Iowa (IA) |
| County | Jones FIPS 19105 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Chicago |
| Population | 395 |
| Coordinates | 42.141680, -90.983070 |
How ZIP+4 works in 52321
The four digits after the hyphen encode a delivery segment inside 52321. 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 52321 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 52321.
| ZIP | City | Distance |
|---|---|---|
| 52309 | Monmouth, IA | 5 mi |
| 52362 | Wyoming, IA | 5.8 mi |
| 52212 | Center Junction, IA | 5.9 mi |
| 52207 | Baldwin, IA | 8.5 mi |
| 52033 | Cascade, IA | 9.6 mi |
| 52323 | Oxford Junction, IA | 11 mi |
| 52310 | Monticello, IA | 12.2 mi |
| 52032 | Bernard, IA | 12.5 mi |
| 52320 | Olin, IA | 12.9 mi |
| 52252 | Langworthy, IA | 13.1 mi |
| 52205 | Anamosa, IA | 15.7 mi |
| 52060 | Maquoketa, IA | 15.8 mi |
Questions about 52321
What is the ZIP+4 code for 52321?
52321 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 52321, you need to look up a specific street address to get them.
What city is 52321?
52321 is assigned to Onslow, Iowa, in Jones 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.