| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Newcastle | 1 | 16,430 | 11,170 | 5.64% | 274 | 60 | City |
| Blanchard | 2 | 10,334 | 8,938 | 2.31% | 339 | 30 | City |
| Purcell | 3 | 7,082 | 6,649 | 1.03% | 464 | 15 | City |
| Dibble | 4 | 1,032 | 890 | 2.38% | 138 | 7 | Town |
| Washington | 5 | 797 | 707 | 1.92% | 550 | 1 | Town |
| Wayne | 6 | 693 | 623 | 1.76% | 1,824 | 0 | Town |
| Byars | 7 | 212 | 188 | 1.92% | 138 | 2 | Town |
Newcastle is the largest city in McClain County, with a population of 16,430.
Byars is the smallest city in McClain County, with a population of 212.
There are 7 cities in McClain County, Oklahoma.