14 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Newcastle | 1 | 15,553 | 10,989 | 5.97% | 259 | 60 | City |
| Newcastle | 2 | 15,553 | 11,170 | 5.97% | 259 | 60 | City |
| Blanchard | 3 | 10,101 | 8,873 | 2.35% | 332 | 30 | City |
| Blanchard | 4 | 10,101 | 8,938 | 2.35% | 332 | 30 | City |
| Purcell | 5 | 7,010 | 6,658 | 1.04% | 460 | 15 | City |
| Purcell | 6 | 7,010 | 6,649 | 1.04% | 460 | 15 | City |
| Dibble | 7 | 1,008 | 889 | 2.34% | 135 | 7 | Town |
| Dibble | 8 | 1,008 | 890 | 2.34% | 135 | 7 | Town |
| Washington | 9 | 782 | 706 | 1.96% | 540 | 1 | Town |
| Washington | 10 | 782 | 707 | 1.96% | 540 | 1 | Town |
| Wayne | 11 | 681 | 622 | 1.64% | 1,792 | 0 | Town |
| Wayne | 12 | 681 | 623 | 1.64% | 1,792 | 0 | Town |
| Byars | 13 | 208 | 188 | 1.96% | 136 | 2 | Town |
| Byars | 14 | 208 | 188 | 1.96% | 136 | 2 | Town |
Newcastle is the largest city in McClain County, with a population of 15,553.
Byars is the smallest city in McClain County, with a population of 208.
There are 14 cities in McClain County, Oklahoma.