15 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Demopolis | 1 | 6,619 | 7,168 | -1.56% | 373 | 18 | City |
| Demopolis | 2 | 6,619 | 7,142 | -1.56% | 373 | 18 | City |
| Linden | 3 | 1,786 | 1,934 | -1.6% | 499 | 4 | City |
| Linden | 4 | 1,786 | 1,928 | -1.6% | 499 | 4 | City |
| Thomaston | 5 | 307 | 326 | -1.29% | 153 | 2 | Town |
| Thomaston | 6 | 307 | 325 | -1.29% | 153 | 2 | Town |
| Sweet Water | 7 | 213 | 229 | -1.39% | 91 | 2 | Town |
| Sweet Water | 8 | 213 | 228 | -1.39% | 91 | 2 | Town |
| Yellow Bluff | 9 | 207 | 227 | -1.9% | 331 | 1 | Town |
| Yellow Bluff | 10 | 207 | 225 | -1.9% | 331 | 1 | Town |
| Faunsdale | 11 | 80 | 87 | -2.44% | 289 | 0 | Town |
| Faunsdale | 12 | 80 | 87 | -2.44% | 289 | 0 | Town |
| Myrtlewood | 13 | 67 | 72 | -1.47% | 26 | 3 | Town |
| Myrtlewood | 14 | 67 | 72 | -1.47% | 26 | 3 | Town |
| Nanafalia | 15 | 29 | 32 | 7.41% | 13 | 2 | CDP |
Demopolis is the largest city in Marengo County, with a population of 6,619.
Nanafalia is the smallest city in Marengo County, with a population of 29.
There are 15 cities in Marengo County, Alabama.