7 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| St. Helens | 1 | 14,737 | 13,905 | 0.95% | 3,019 | 5 | City |
| Scappoose | 2 | 8,413 | 8,019 | 0.79% | 2,448 | 3 | City |
| Vernonia | 3 | 2,452 | 2,380 | 0.49% | 1,492 | 2 | City |
| Columbia City | 4 | 1,946 | 1,954 | -0.05% | 2,479 | 1 | City |
| Rainier | 5 | 1,944 | 1,907 | 0.31% | 476 | 4 | City |
| Clatskanie | 6 | 1,812 | 1,722 | 0.83% | 1,394 | 1 | City |
| Prescott | 7 | 82 | 81 | 0% | 1,188 | 0 | City |
St. Helens is the largest city in Columbia County, with a population of 14,737.
Prescott is the smallest city in Columbia County, with a population of 82.
There are 7 cities in Columbia County, Oregon.