Founded in 1875, Columbia County is one of 39 counties in the state of Washington. Historically, Columbia County was formed from Walla Walla County. The city of Dayton is the county seat. With FIPS code of 13, Columbia County has a population of 3,952 and area of 869 square miles (2,251 km2).
List of all cities in Columbia County, WA alphabetically
| City/Town | Postal Code | Area Code |
| Dayton, WA | 99328 | 509 |
| Starbuck, WA | 99359 | 509 |