7 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Eureka | 1 | 24,882 | 26,471 | -1.05% | 2,601 | 10 | City |
| Arcata | 2 | 18,703 | 18,837 | -0.12% | 1,986 | 9 | City |
| Fortuna | 3 | 11,923 | 12,495 | -0.79% | 2,270 | 5 | City |
| Rio Dell | 4 | 3,194 | 3,388 | -0.99% | 1,286 | 2 | City |
| Ferndale | 5 | 1,342 | 1,399 | -0.67% | 1,113 | 1 | City |
| Blue Lake | 6 | 1,133 | 1,211 | -1.13% | 1,833 | 1 | City |
| Trinidad | 7 | 313 | 337 | -1.26% | 641 | 0 | City |
Eureka is the largest city in Humboldt County, with a population of 24,882.
Trinidad is the smallest city in Humboldt County, with a population of 313.
There are 7 cities in Humboldt County, California.