ZIP Code 99328 — Dayton, WA
99328 is a standard (street delivery) ZIP code serving Dayton, Washington, 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 99328 at a glance
| ZIP code | 99328 |
|---|---|
| Primary city | Dayton |
| State | Washington (WA) |
| County | Columbia FIPS 53013 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Los_Angeles |
| Population | 3,646 |
| Coordinates | 46.269370, -117.879560 |
How ZIP+4 works in 99328
The four digits after the hyphen encode a delivery segment inside 99328. 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 99328 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 99328.
| ZIP | City | Distance |
|---|---|---|
| 99361 | Waitsburg, WA | 12.8 mi |
| 99329 | Dixie, WA | 15.6 mi |
| 99347 | Pomeroy, WA | 18.2 mi |
| 99359 | Starbuck, WA | 22.5 mi |
| 99362 | Walla Walla, WA | 24.2 mi |
| 99136 | Hay, WA | 28.2 mi |
| 99348 | Prescott, WA | 28.3 mi |
| 99324 | College Place, WA | 28.7 mi |
| 99333 | Hooper, WA | 31.3 mi |
| 97862 | Milton Freewater, OR | 31.5 mi |
| 99143 | Lacrosse, WA | 32.9 mi |
| 97886 | Weston, OR | 37.1 mi |
Questions about 99328
What is the ZIP+4 code for 99328?
99328 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 99328, you need to look up a specific street address to get them.
What city is 99328?
99328 is assigned to Dayton, Washington, 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.