ZIP Code 51010 — Castana, IA
51010 is a standard (street delivery) ZIP code serving Castana, Iowa, in Monona 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 51010 at a glance
| ZIP code | 51010 |
|---|---|
| Primary city | Castana |
| State | Iowa (IA) |
| County | Monona FIPS 19133 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Chicago |
| Population | 425 |
| Coordinates | 42.093090, -95.920440 |
How ZIP+4 works in 51010
The four digits after the hyphen encode a delivery segment inside 51010. 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 51010 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 51010.
| ZIP | City | Distance |
|---|---|---|
| 51051 | Rodney, IA | 8.1 mi |
| 51034 | Mapleton, IA | 8.2 mi |
| 51040 | Onawa, IA | 8.8 mi |
| 51572 | Soldier, IA | 9.8 mi |
| 51056 | Smithland, IA | 9.9 mi |
| 51060 | Ute, IA | 11.9 mi |
| 51558 | Moorhead, IA | 12.6 mi |
| 51026 | Hornick, IA | 13.4 mi |
| 51063 | Whiting, IA | 13.9 mi |
| 51044 | Oto, IA | 14.4 mi |
| 51523 | Blencoe, IA | 14.7 mi |
| 51019 | Danbury, IA | 15.9 mi |
Questions about 51010
What is the ZIP+4 code for 51010?
51010 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 51010, you need to look up a specific street address to get them.
What city is 51010?
51010 is assigned to Castana, Iowa, in Monona 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.