26 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 | 1,134 | 1,125 | 0.09% | 55 | 21 | Township |
| Centropolis | 4 | 1,048 | 1,025 | 0.38% | 26 | 41 | Township |
| Pomona | 5 | 893 | 887 | 0.11% | 946 | 1 | City |
| Ottawa | 6 | 845 | 823 | 0.48% | 20 | 42 | Township |
| Cutler | 7 | 821 | 795 | 0.61% | 19 | 43 | Township |
| Richmond | 8 | 803 | 814 | -0.37% | 23 | 35 | Township |
| Ohio | 9 | 762 | 745 | 0.13% | 18 | 42 | Township |
| Williamsburg | 10 | 701 | 703 | -0.28% | 13 | 56 | Township |
| Peoria | 11 | 679 | 655 | 0.44% | 19 | 35 | Township |
| Pottawatomie | 12 | 608 | 591 | 0.5% | 16 | 39 | Township |
| Homewood | 13 | 557 | 543 | 0.36% | 19 | 30 | Township |
| Richmond | 14 | 478 | 497 | -0.42% | 14 | 34 | Township |
| Harrison | 15 | 455 | 442 | 0.44% | 18 | 25 | Township |
| Hayes | 16 | 446 | 433 | 0.68% | 15 | 30 | Township |
| Richmond | 17 | 434 | 448 | -0.46% | 1,273 | 0 | City |
| Greenwood | 18 | 400 | 390 | 0.5% | 13 | 30 | Township |
| Williamsburg | 19 | 383 | 389 | -0.26% | 392 | 1 | City |
| Appanoose | 20 | 323 | 319 | 0% | 11 | 30 | Township |
| Princeton | 21 | 253 | 247 | 0.4% | 749 | 0 | City |
| Lane | 22 | 245 | 239 | 0.41% | 1,052 | 0 | City |
| Rantoul | 23 | 176 | 169 | 0.57% | 1,197 | 0 | City |
| Lane | 24 | 104 | 106 | 0% | 3 | 36 | Township |
| Lane | 25 | 74 | 77 | -1.33% | 1 | 53 | Township |
| Ottawa | 26 | 42 | 36 | 5% | 1 | 36 | Township |
Ottawa is the largest city in Franklin County, with a population of 12,783.
Ottawa is the smallest city in Franklin County, with a population of 42.
There are 26 cities in Franklin County, Kansas.