| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Lewistown | 1 | 8,343 | 8,557 | -0.5% | 4,110 | 2 | Borough |
| Granville | 2 | 4,641 | 4,642 | 0.35% | 115 | 40 | Township |
| Brown | 3 | 4,203 | 4,118 | 0.38% | 128 | 33 | Township |
| Union | 4 | 3,700 | 3,645 | 0.43% | 145 | 25 | Township |
| Decatur | 5 | 2,945 | 2,968 | 0.07% | 65 | 45 | Township |
| Menno | 6 | 2,048 | 1,987 | 0.64% | 86 | 24 | Township |
| Burnham | 7 | 1,964 | 1,992 | -0.3% | 1,867 | 1 | Borough |
| Bratton | 8 | 1,179 | 1,193 | -0.17% | 36 | 33 | Township |
| Granville | 9 | 879 | 883 | 0% | 36 | 25 | Township |
| McClure | 10 | 878 | 891 | -0.23% | 234 | 4 | Borough |
| Juniata Terrace | 11 | 547 | 562 | -0.55% | 3,256 | 0 | Borough |
| McVeytown | 12 | 332 | 340 | -0.6% | 3,495 | 0 | Borough |
| Newton Hamilton | 13 | 203 | 194 | 0% | 1,310 | 0 | Borough |
Lewistown is the largest city in Mifflin County, with a population of 8,343.
Newton Hamilton is the smallest city in Mifflin County, with a population of 203.
There are 13 cities in Mifflin County, Pennsylvania.