10 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Longview | 1 | 37,962 | 37,869 | 0.05% | 2,565 | 14.80 | City |
| Kelso | 2 | 12,592 | 12,731 | -0.22% | 1,548 | 8.13 | City |
| Woodland | 3 | 6,460 | 6,542 | -0.25% | 1,571 | 4.11 | City |
| Lexington | 4 | 5,686 | 3,785 | 7.14% | 4,246 | 1.34 | CDP |
| Longview Heights | 5 | 4,286 | 4,388 | 0.68% | 1,030 | 4.16 | CDP |
| Kalama | 6 | 3,073 | 2,973 | 0.66% | 853 | 3.60 | City |
| Beacon Hill | 7 | 2,653 | 1,903 | 7.15% | 2,309 | 1.15 | CDP |
| Castle Rock | 8 | 2,427 | 2,452 | -0.21% | 1,158 | 2.10 | City |
| Ryderwood | 9 | 432 | 401 | 0.47% | 2,683 | 0.16 | CDP |
| Cougar | 10 | 41 | 93 | 7.89% | 71 | 0.58 | CDP |
Longview is the largest city in Cowlitz County, with a population of 37,962.
Cougar is the smallest city in Cowlitz County.
There are 10 cities in Cowlitz County, Washington.