ZIP Code 18631 — Mifflinville, PA
18631 is a standard (street delivery) ZIP code serving Mifflinville, Pennsylvania, in Columbia 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 18631 at a glance
| ZIP code | 18631 |
|---|---|
| Primary city | Mifflinville |
| State | Pennsylvania (PA) |
| County | Columbia FIPS 42037 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 1,100 |
| Coordinates | 41.030790, -76.302330 |
How ZIP+4 works in 18631
The four digits after the hyphen encode a delivery segment inside 18631. 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 18631 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 18631.
| ZIP | City | Distance |
|---|---|---|
| 18603 | Berwick, PA | 4.8 mi |
| 18635 | Nescopeck, PA | 5 mi |
| 17815 | Bloomsburg, PA | 6.7 mi |
| 18246 | Rock Glen, PA | 7.5 mi |
| 17859 | Orangeville, PA | 7.7 mi |
| 17985 | Zion Grove, PA | 8.4 mi |
| 18241 | Nuremberg, PA | 9.3 mi |
| 17878 | Stillwater, PA | 9.8 mi |
| 18249 | Sugarloaf, PA | 10 mi |
| 18256 | Weston, PA | 10.2 mi |
| 17820 | Catawissa, PA | 10.5 mi |
| 18655 | Shickshinny, PA | 11.9 mi |
Questions about 18631
What is the ZIP+4 code for 18631?
18631 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 18631, you need to look up a specific street address to get them.
What city is 18631?
18631 is assigned to Mifflinville, Pennsylvania, in Columbia 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.