5 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Longview | 1 | 38,400 | 37,869 | 0.28% | 2,595 | 15 | City |
| Kelso | 2 | 12,738 | 12,732 | 0.01% | 1,566 | 8 | City |
| Woodland | 3 | 6,483 | 6,547 | -0.2% | 1,577 | 4 | City |
| Kalama | 4 | 3,170 | 2,973 | 1.25% | 880 | 4 | City |
| Castle Rock | 5 | 2,443 | 2,451 | -0.08% | 1,166 | 2 | City |
Longview is the largest city in Cowlitz County, with a population of 38,400.
Castle Rock is the smallest city in Cowlitz County, with a population of 2,443.
There are 5 cities in Cowlitz County, Washington.