| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Eureka | 1 | 25,044 | 26,471 | -1.03% | 2,618 | 10 | City |
| Arcata | 2 | 19,029 | 18,838 | -0.09% | 2,021 | 9 | City |
| Fortuna | 3 | 11,904 | 12,491 | -0.82% | 2,267 | 5 | City |
| Rio Dell | 4 | 3,178 | 3,383 | -1.03% | 1,279 | 2 | City |
| Ferndale | 5 | 1,338 | 1,399 | -0.74% | 1,109 | 1 | City |
| Blue Lake | 6 | 1,130 | 1,212 | -1.22% | 1,828 | 1 | City |
| Trinidad | 7 | 313 | 337 | -1.26% | 641 | 0 | City |
Eureka is the largest city in Humboldt County, with a population of 25,044.
Trinidad is the smallest city in Humboldt County, with a population of 313.
There are 7 cities in Humboldt County, California.