33 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Chambersburg | 1 | 23,331 | 21,879 | 1.26% | 3,369 | 7 | Borough |
| Greene | 2 | 18,664 | 18,435 | 0.16% | 326 | 57 | Township |
| Concord | 3 | 18,603 | 18,276 | 0.83% | 1,365 | 14 | Township |
| Antrim | 4 | 16,473 | 15,801 | 1.07% | 235 | 70 | Township |
| Guilford | 5 | 15,229 | 14,654 | 1.16% | 298 | 51 | Township |
| Waynesboro | 6 | 11,119 | 11,029 | 0.16% | 3,241 | 3 | Borough |
| St. Thomas | 7 | 6,008 | 5,915 | 0.23% | 116 | 52 | Township |
| Quincy | 8 | 5,301 | 5,305 | -0.11% | 117 | 45 | Township |
| Peters | 9 | 4,469 | 4,465 | -0.02% | 80 | 56 | Township |
| Guilford | 10 | 4,409 | 3,571 | 3.55% | 2,846 | 2 | CDP |
| Greencastle | 11 | 4,225 | 4,228 | -0.02% | 2,661 | 2 | Borough |
| State Line | 12 | 3,566 | 3,548 | 1.62% | 1,302 | 3 | CDP |
| Wayne Heights | 13 | 3,297 | 2,605 | 1.54% | 1,544 | 2 | CDP |
| Fayetteville | 14 | 2,649 | 2,855 | -1.19% | 812 | 3 | CDP |
| Letterkenny | 15 | 2,557 | 2,462 | 1.15% | 36 | 70 | Township |
| Fannett | 16 | 2,494 | 2,486 | -0.12% | 37 | 68 | Township |
| Lurgan | 17 | 2,193 | 2,206 | -0.09% | 67 | 33 | Township |
| Marion | 18 | 1,969 | 1,841 | 0.61% | 131 | 15 | Township |
| Metal | 19 | 1,759 | 1,759 | -0.23% | 39 | 45 | Township |
| Mont Alto | 20 | 1,560 | 1,575 | -0.19% | 2,771 | 1 | Borough |
| Mercersburg | 21 | 1,490 | 1,505 | -0.2% | 1,652 | 1 | Borough |
| Concord | 22 | 1,362 | 1,410 | -0.44% | 56 | 24 | Township |
| Concord | 23 | 1,256 | 1,279 | -0.08% | 38 | 33 | Township |
| Pen Mar | 24 | 1,239 | 1,185 | 1.72% | 1,677 | 1 | CDP |
| Marion | 25 | 1,207 | 1,186 | 0.33% | 55 | 22 | Township |
| Marion | 26 | 1,169 | 1,551 | 1.21% | 587 | 2 | CDP |
| Scotland | 27 | 1,125 | 734 | -1.57% | 1,365 | 1 | CDP |
| Marion | 28 | 1,120 | 1,152 | -0.71% | 44 | 25 | Township |
| Fort Loudon | 29 | 1,102 | 1,168 | 1.29% | 259 | 4 | CDP |
| Blue Ridge Summit | 30 | 1,076 | 680 | 1.13% | 1,466 | 1 | CDP |
| Marion | 31 | 790 | 798 | 0% | 77 | 10 | Township |
| Rouzerville | 32 | 607 | 746 | -3.34% | 922 | 1 | CDP |
| Orrstown | 33 | 212 | 214 | -0.47% | 3,313 | 0 | Borough |
Chambersburg is the largest city in Franklin County, with a population of 23,331.
Orrstown is the smallest city in Franklin County, with a population of 212.
There are 33 cities in Franklin County, Pennsylvania.