Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Pop. | 2020 Pop. | Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Chambersburg | 1 | 22,364 | 21,886 | 0.53% | 3,229 | 6.9 | Borough |
| Greene township | 2 | 18,666 | 18,438 | 0.4% | 326 | 57.3 | Township |
| Concord township | 3 | 18,209 | 18,269 | 0.14% | 1,337 | 13.6 | Township |
| Antrim township | 4 | 16,259 | 15,786 | 1.04% | 232 | 70.1 | Township |
| Guilford township | 5 | 14,946 | 14,636 | 0.62% | 292 | 51.2 | Township |
| Waynesboro | 6 | 11,077 | 11,035 | 0.09% | 3,229 | 3.4 | Borough |
| St. Thomas township | 7 | 6,010 | 5,914 | 0.67% | 116 | 51.9 | Township |
| Quincy township | 8 | 5,299 | 5,296 | 0.08% | 117 | 45.2 | Township |
| Peters township | 9 | 4,486 | 4,461 | 0.4% | 80 | 55.8 | Township |
| Greencastle | 10 | 4,244 | 4,244 | 0% | 2,673 | 1.6 | Borough |
| Letterkenny township | 11 | 2,520 | 2,460 | 0.8% | 36 | 70.4 | Township |
| Fannett township | 12 | 2,505 | 2,485 | 0.36% | 37 | 68.2 | Township |
| Lurgan township | 13 | 2,194 | 2,207 | -0.09% | 67 | 32.7 | Township |
| Marion township | 14 | 1,935 | 1,841 | 0.1% | 128 | 15.1 | Township |
| Metal township | 15 | 1,769 | 1,759 | 0.11% | 40 | 44.5 | Township |
| Mont Alto | 16 | 1,569 | 1,584 | -0.25% | 2,787 | 0.6 | Borough |
| Mercersburg | 17 | 1,492 | 1,506 | -0.27% | 1,654 | 0.9 | Borough |
| Concord township | 18 | 1,365 | 1,410 | -0.66% | 56 | 24.2 | Township |
| Concord township | 19 | 1,254 | 1,279 | -0.32% | 38 | 33.0 | Township |
| Marion township | 20 | 1,179 | 1,184 | -0.51% | 54 | 22.0 | Township |
| Marion township | 21 | 1,138 | 1,151 | 0.53% | 45 | 25.4 | Township |
| Orrstown | 22 | 212 | 214 | -0.47% | 3,313 | 0.1 | Borough |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Chambersburg is the largest city in Franklin County.
Orrstown is the smallest city in Franklin County.
There are 22 cities in Franklin County, Pennsylvania.