22 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Chambersburg | 1 | 22,484 | 21,886 | 0.54% | 3,247 | 6.92 | Borough |
| Greene township | 2 | 18,741 | 18,438 | 0.4% | 327 | 57.30 | Township |
| Concord township | 3 | 18,235 | 18,269 | 0.14% | 1,338 | 13.62 | Township |
| Antrim township | 4 | 16,427 | 15,786 | 1.03% | 234 | 70.09 | Township |
| Guilford township | 5 | 15,038 | 14,636 | 0.62% | 294 | 51.17 | Township |
| Waynesboro | 6 | 11,088 | 11,035 | 0.1% | 3,232 | 3.43 | Borough |
| St. Thomas township | 7 | 6,050 | 5,914 | 0.67% | 117 | 51.87 | Township |
| Quincy township | 8 | 5,303 | 5,296 | 0.07% | 117 | 45.20 | Township |
| Peters township | 9 | 4,504 | 4,461 | 0.4% | 81 | 55.81 | Township |
| Greencastle | 10 | 4,244 | 4,244 | 0% | 2,673 | 1.59 | Borough |
| Letterkenny township | 11 | 2,540 | 2,460 | 0.79% | 36 | 70.38 | Township |
| Fannett township | 12 | 2,514 | 2,485 | 0.36% | 37 | 68.20 | Township |
| Lurgan township | 13 | 2,192 | 2,207 | -0.09% | 67 | 32.72 | Township |
| Marion township | 14 | 1,937 | 1,841 | 0.1% | 128 | 15.08 | Township |
| Metal township | 15 | 1,771 | 1,759 | 0.11% | 40 | 44.53 | Township |
| Mont Alto | 16 | 1,565 | 1,584 | -0.26% | 2,780 | 0.56 | Borough |
| Mercersburg | 17 | 1,489 | 1,506 | -0.2% | 1,651 | 0.90 | Borough |
| Concord township | 18 | 1,356 | 1,410 | -0.66% | 56 | 24.18 | Township |
| Concord township | 19 | 1,250 | 1,279 | -0.32% | 38 | 33.05 | Township |
| Marion township | 20 | 1,173 | 1,184 | -0.51% | 53 | 21.98 | Township |
| Marion township | 21 | 1,144 | 1,151 | 0.53% | 45 | 25.35 | Township |
| Orrstown | 22 | 212 | 214 | 0% | 3,313 | 0.06 | Borough |
Chambersburg is the largest city in Franklin County, with a population of 22,484.
Orrstown is the smallest city in Franklin County.
There are 22 cities in Franklin County, Pennsylvania.