2 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Friday Harbor | 1 | 2,806 | 2,631 | 1.26% | 1,283 | 2.19 | Town |
| Roche Harbor | 2 | 941 | 615 | 7.17% | 234 | 4.02 | CDP |
Friday Harbor is the largest city in San Juan County, with a population of 2,806.
Roche Harbor is the smallest city in San Juan County.
There are 2 cities in San Juan County, Washington.