11 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| California | 1 | 14,079 | 14,730 | 1.06% | 1,094 | 13 | CDP |
| Lexington Park | 2 | 14,015 | 12,934 | 1.15% | 2,311 | 6 | CDP |
| Wildewood | 3 | 9,295 | 6,691 | 7.15% | 3,289 | 3 | CDP |
| Leonardtown | 4 | 5,166 | 4,515 | 2.48% | 1,342 | 4 | Town |
| Leonardtown | 5 | 5,166 | 4,541 | 2.48% | 1,342 | 4 | Town |
| Mechanicsville | 6 | 1,852 | 1,724 | 1.26% | 357 | 5 | CDP |
| Callaway | 7 | 1,520 | 1,320 | 7.12% | 319 | 5 | CDP |
| Charlotte Hall | 8 | 1,408 | 1,740 | 0% | 278 | 5 | CDP |
| Piney Point | 9 | 1,075 | 1,036 | 1.32% | 717 | 2 | CDP |
| Tall Timbers | 10 | 484 | 570 | 0.21% | 358 | 1 | CDP |
| St. George Island | 11 | 196 | 426 | -2% | 249 | 1 | CDP |
California is the largest city in St. Mary's County, with a population of 14,079.
St. George Island is the smallest city in St. Mary's County, with a population of 196.
There are 11 cities in St. Mary's County, Maryland.