7 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Eureka | 1 | 25,147 | 26,471 | -1.04% | 2,629 | 10 | City |
| Arcata | 2 | 18,725 | 18,837 | -0.12% | 1,989 | 9 | City |
| Fortuna | 3 | 12,018 | 12,495 | -0.79% | 2,288 | 5 | City |
| Rio Dell | 4 | 3,226 | 3,388 | -1.01% | 1,299 | 2 | City |
| Ferndale | 5 | 1,351 | 1,399 | -0.73% | 1,120 | 1 | City |
| Blue Lake | 6 | 1,146 | 1,211 | -1.12% | 1,854 | 1 | City |
| Trinidad | 7 | 317 | 337 | -1.25% | 650 | 0 | City |
Eureka is the largest city in Humboldt County, with a population of 25,147.
Trinidad is the smallest city in Humboldt County, with a population of 317.
There are 7 cities in Humboldt County, California.