6 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Dallas | 1 | 18,138 | 17,000 | 1.27% | 3,693 | 5 | City |
| Monmouth | 2 | 11,777 | 11,144 | 1.08% | 5,260 | 2 | City |
| Independence | 3 | 10,368 | 10,001 | 0.71% | 3,464 | 3 | City |
| Grand Ronde | 4 | 1,347 | 1,479 | -1.54% | 70 | 19 | CDP |
| Falls City | 5 | 1,057 | 1,056 | 0% | 879 | 1 | City |
| Fort Hill | 6 | 49 | 101 | -9.26% | 34 | 1 | CDP |
Dallas is the largest city in Polk County, with a population of 18,138.
Fort Hill is the smallest city in Polk County, with a population of 49.
There are 6 cities in Polk County, Oregon.