8 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Ottawa | 1 | 12,783 | 12,633 | 0.2% | 1,199 | 11 | City |
| Wellsville | 2 | 1,926 | 1,946 | -0.16% | 1,120 | 2 | City |
| Pomona | 3 | 893 | 887 | 0.11% | 946 | 1 | City |
| Richmond | 4 | 434 | 448 | -0.46% | 1,273 | 0 | City |
| Williamsburg | 5 | 383 | 389 | -0.26% | 392 | 1 | City |
| Princeton | 6 | 253 | 247 | 0.4% | 749 | 0 | City |
| Lane | 7 | 245 | 239 | 0.41% | 1,052 | 0 | City |
| Rantoul | 8 | 176 | 169 | 0.57% | 1,197 | 0 | City |
Ottawa is the largest city in Franklin County, with a population of 12,783.
Rantoul is the smallest city in Franklin County, with a population of 176.
There are 8 cities in Franklin County, Kansas.