ZIP Code 98611 — Castle Rock, WA
98611 is a standard (street delivery) ZIP code serving Castle Rock, Washington, in Cowlitz 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 98611 at a glance
| ZIP code | 98611 |
|---|---|
| Primary city | Castle Rock |
| State | Washington (WA) |
| County | Cowlitz FIPS 53015 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Los_Angeles |
| Population | 9,302 |
| Coordinates | 46.306420, -122.904790 |
How ZIP+4 works in 98611
The four digits after the hyphen encode a delivery segment inside 98611. 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 98611 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 98611.
| ZIP | City | Distance |
|---|---|---|
| 98645 | Silverlake, WA | 6.1 mi |
| 98593 | Vader, WA | 8.5 mi |
| 98581 | Ryderwood, WA | 8.6 mi |
| 98632 | Longview, WA | 10.2 mi |
| 98626 | Kelso, WA | 12 mi |
| 98591 | Toledo, WA | 12 mi |
| 98596 | Winlock, WA | 13.3 mi |
| 98609 | Carrolls, WA | 16.3 mi |
| 98538 | Curtis, WA | 16.8 mi |
| 98542 | Ethel, WA | 17.5 mi |
| 98649 | Toutle, WA | 17.7 mi |
| 98565 | Napavine, WA | 18.8 mi |
Questions about 98611
What is the ZIP+4 code for 98611?
98611 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 98611, you need to look up a specific street address to get them.
What city is 98611?
98611 is assigned to Castle Rock, Washington, in Cowlitz 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.