16 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| St. Helens | 1 | 14,598 | 13,843 | 0.95% | 3,009 | 5 | City |
| St. Helens | 2 | 14,598 | 13,905 | 0.95% | 3,009 | 5 | City |
| Scappoose | 3 | 8,347 | 8,010 | 0.78% | 2,429 | 3 | City |
| Scappoose | 4 | 8,347 | 8,019 | 0.78% | 2,429 | 3 | City |
| Vernonia | 5 | 2,440 | 2,375 | 0.49% | 1,485 | 2 | City |
| Vernonia | 6 | 2,440 | 2,380 | 0.49% | 1,485 | 2 | City |
| Columbia City | 7 | 1,947 | 1,951 | -0.1% | 2,480 | 1 | City |
| Columbia City | 8 | 1,947 | 1,954 | -0.1% | 2,480 | 1 | City |
| Rainier | 9 | 1,938 | 1,904 | 0.31% | 475 | 4 | City |
| Rainier | 10 | 1,938 | 1,907 | 0.31% | 475 | 4 | City |
| Clatskanie | 11 | 1,797 | 1,716 | 0.84% | 1,382 | 1 | City |
| Clatskanie | 12 | 1,797 | 1,722 | 0.84% | 1,382 | 1 | City |
| Warren | 13 | 1,563 | 1,876 | -0.95% | 248 | 6 | CDP |
| Deer Island | 14 | 214 | 105 | -2.28% | 439 | 0 | CDP |
| Prescott | 15 | 82 | 81 | 0% | 1,188 | 0 | City |
| Prescott | 16 | 82 | 81 | 0% | 1,188 | 0 | City |
St. Helens is the largest city in Columbia County, with a population of 14,598.
Prescott is the smallest city in Columbia County, with a population of 82.
There are 16 cities in Columbia County, Oregon.