| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| St. Helens | 1 | 14,581 | 13,892 | 0.91% | 2,987 | 5 | City |
| Scappoose | 2 | 8,316 | 8,012 | 0.71% | 2,420 | 3 | City |
| Vernonia | 3 | 2,424 | 2,367 | 0.5% | 1,475 | 2 | City |
| Columbia City | 4 | 1,944 | 1,955 | -0.1% | 2,476 | 1 | City |
| Rainier | 5 | 1,928 | 1,901 | 0.21% | 472 | 4 | City |
| Clatskanie | 6 | 1,792 | 1,723 | 0.73% | 1,378 | 1 | City |
| Prescott | 7 | 81 | 80 | 0% | 1,174 | 0 | City |
St. Helens is the largest city in Columbia County, with a population of 14,581.
Prescott is the smallest city in Columbia County, with a population of 81.
There are 7 cities in Columbia County, Oregon.