Post Offices List in Columbia County, Oregon:
| Clatskanie Post Office | 90 Sw Belair Dr, Clatskanie, OR 97016 |
| Columbia City Post Office | 1905 2nd St, Columbia City, OR 97018 |
| Rainier Post Office | 207 W A St, Rainier, OR 97048 |
| Saint Helens Post Office | 1571 Columbia Blvd, Saint Helens, OR 97051 |
| Scappoose Post Office | 52643 Columbia River Hwy, Scappoose, OR 97056 |
| Vernonia Post Office | 716 Jefferson Ave, Vernonia, OR 97064 |