13 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Weaverville | 1 | 3,578 | 3,308 | -0.03% | 278 | 13 | CDP |
| Hayfork | 2 | 3,442 | 2,586 | 2.14% | 48 | 72 | CDP |
| Lewiston | 3 | 2,474 | 1,481 | 3.56% | 124 | 20 | CDP |
| Junction City | 4 | 1,324 | 754 | 3.36% | 50 | 27 | CDP |
| Douglas City | 5 | 1,200 | 678 | 2.74% | 39 | 30 | CDP |
| Trinity Village | 6 | 651 | 248 | 3.83% | 162 | 4 | CDP |
| Salyer | 7 | 619 | 433 | 7.09% | 117 | 5 | CDP |
| Hyampom | 8 | 350 | 124 | 2.34% | 17 | 20 | CDP |
| Mad River | 9 | 297 | 341 | -2.94% | 8 | 35 | CDP |
| Coffee Creek | 10 | 293 | 187 | 1.74% | 25 | 12 | CDP |
| Trinity Center | 11 | 246 | 265 | -0.4% | 47 | 5 | CDP |
| Burnt Ranch | 12 | 215 | 185 | -1.83% | 16 | 13 | CDP |
| Post Mountain | 13 | 126 | 82 | 6.78% | 10 | 12 | CDP |
Weaverville is the largest city in Trinity County, with a population of 3,578.
Post Mountain is the smallest city in Trinity County, with a population of 126.
There are 13 cities in Trinity County, California.