9 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| St. Helens | 1 | 14,785 | 13,915 | 1.19% | 3,048 | 4.85 | City |
| Scappoose | 2 | 8,419 | 8,019 | 0.96% | 2,450 | 3.44 | City |
| Vernonia | 3 | 2,455 | 2,379 | 0.61% | 1,494 | 1.64 | City |
| Columbia City | 4 | 1,938 | 1,952 | -0.15% | 2,469 | 0.79 | City |
| Rainier | 5 | 1,938 | 1,908 | 0.31% | 475 | 4.08 | City |
| Clatskanie | 6 | 1,773 | 1,722 | 0.57% | 1,364 | 1.30 | City |
| Warren | 7 | 1,563 | 1,876 | -0.95% | 248 | 6.31 | CDP |
| Deer Island | 8 | 214 | 105 | -2.28% | 439 | 0.49 | CDP |
| Prescott | 9 | 80 | 79 | 0% | 1,159 | 0.07 | City |
St. Helens is the largest city in Columbia County, with a population of 14,785.
Prescott is the smallest city in Columbia County.
There are 9 cities in Columbia County, Oregon.