Founded in 1854, Cowlitz County is one of 39 counties in the state of Washington. Historically, Cowlitz County was formed from Lewis County. The city of Kelso is the county seat. With FIPS code of 15, Cowlitz County has a population of 110,730 and area of 1,139 square miles (2,950 km2).
List of all cities in Cowlitz County, WA alphabetically
| City/Town | Postal Code | Area Code |
| Ariel, WA | 98603 | 360/564 |
| Carrolls, WA | 98609 | 360/564 |
| Castle Rock, WA | 98611 | 360/564 |
| Cougar, WA | 98616 | 360/564 |
| Kalama, WA | 98625 | 360/564 |
| Kelso, WA | 98626 | 360/564 |
| Longview, WA | 98632 | 360/564 |
| Ryderwood, WA | 98581 | 360/564 |
| Silverlake, WA | 98645 | 360/564 |
| Toutle, WA | 98645 | 360/564 |
| Toutle, WA | 98649 | 360/564 |
| Woodland, WA | 98674 | 360/564 |
| Yale, WA | 98603 | 360/564 |