5 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Longview | 1 | 38,506 | 37,869 | 0.28% | 2,602 | 15 | City |
| Kelso | 2 | 12,739 | 12,732 | 0.01% | 1,566 | 8 | City |
| Woodland | 3 | 6,470 | 6,547 | -0.2% | 1,573 | 4 | City |
| Kalama | 4 | 3,210 | 2,973 | 1.26% | 891 | 4 | City |
| Castle Rock | 5 | 2,442 | 2,451 | -0.04% | 1,166 | 2 | City |
Longview is the largest city in Cowlitz County, with a population of 38,506.
Castle Rock is the smallest city in Cowlitz County, with a population of 2,442.
There are 5 cities in Cowlitz County, Washington.