5 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Morgan City | 1 | 10,514 | 11,411 | -1.4% | 1,757 | 6 | City |
| Franklin | 2 | 6,091 | 6,670 | -1.55% | 611 | 10 | City |
| Patterson | 3 | 5,467 | 5,907 | -1.32% | 2,166 | 3 | City |
| Berwick | 4 | 4,370 | 4,744 | -1.4% | 741 | 6 | Town |
| Baldwin | 5 | 1,624 | 1,747 | -1.22% | 505 | 3 | Town |
Morgan City is the largest city in St. Mary Parish, with a population of 10,514.
Baldwin is the smallest city in St. Mary Parish, with a population of 1,624.
There are 5 cities in St. Mary Parish, Louisiana.