St. Mary Parish, Louisiana
A parish in Louisiana, ranked 23 of 64 by population.
ParishFIPS 22101
- Population
- 46,552
- -2,597 (-5.3%) since 2020
- Land area
- 558.5
- square miles. A further 50.1% of the total area is water
- Population density
- 83.3
- people per square mile, computed rather than published
- County seat
- Franklin
- Seat of county government.
- Established
- 1811
- 214 years ago
- Largest city
- Morgan City city
- Population 10,757 for the whole place, which extends beyond this parish.
Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; Wikidata (CC0), Wikidata. Retrieved 30 August 2026.
Satellite view
Aerial imagery of St. Mary Parish with its boundary drawn on top. A map shows you the shape; this shows you what is inside it, and which side of the line a place falls on.
Where St. Mary Parish ranks
Position among the 64 parishes of Louisiana, and among all 3,144 US counties and county-equivalents. Computed from the figures on this page.
| Measure | Value | In Louisiana | Nationally |
|---|---|---|---|
| Population | 46,552 | 23rd of 64 | 1,062nd of 3,144 |
| Land area | 558.5 sq mi | 43rd of 64 | 1,857th of 3,144 |
| Population density | 83.3 per sq mi | 24th of 64 | 1,044th of 3,144 |
| Median household income | $52,576 | 35th of 64 | 2,626th of 3,143 |
Full data for St. Mary Parish
| Measure | Value | Source and vintage |
|---|---|---|
| Population | 46,552 | Vintage 2025 Population Estimates |
| Population in 2020 | 49,149 | Vintage 2025 Population Estimates |
| 2020 estimates base? | 49,405 | Vintage 2025 Population Estimates |
| Land area | 558.5 sq mi | 2025 Gazetteer Files |
| Water area | 561.2 sq mi | 2025 Gazetteer Files |
| Total area | 1,120 sq mi | 2025 Gazetteer Files |
| Population density? | 83.3 per sq mi | Computed: Vintage 2025 estimates divided by 2025 Gazetteer land area |
| Median household income | $52,576 | American Community Survey 2020-2024 5-Year Estimates |
| Median home value | $138,900 | American Community Survey 2020-2024 5-Year Estimates |
| Median age | 39.7 | American Community Survey 2020-2024 5-Year Estimates |
| Households | 18,463 | American Community Survey 2020-2024 5-Year Estimates |
| Housing units | 22,507 | American Community Survey 2020-2024 5-Year Estimates |
Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026. Population density is computed here, not published: it divides the Vintage 2025 population estimate by the 2025 Gazetteer land area, which are two different Census products. Retrieved 30 August 2026.
How the population changed
The Census Bureau publishes the components behind an estimate, not just the total. For the year to July 2025:
- Births minus deaths
- -53
- 551 births, 604 deaths
- Net migration
- -366
- More people moved out than moved in.
Source: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026. Retrieved 30 August 2026.
The 4 areas bordering St. Mary Parish
Ordered by the length of the border actually shared, which the Census Bureau publishes in its county adjacency file and which no other county reference presents.
| Bordering area | State | Shared border | Population |
|---|---|---|---|
| Iberia Parish | Louisiana | 72 mi | 66,846 |
| Terrebonne Parish | Louisiana | 50 mi | 104,163 |
| St. Martin Parish | Louisiana | 33 mi | 51,106 |
| Assumption Parish | Louisiana | 6.1 mi | 19,720 |
Source: US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. Retrieved 30 August 2026.
All 64 parishes of Louisiana
Open the interactive Louisiana county map, or jump straight to any of them.
- Acadia Parish
- Allen Parish
- Ascension Parish
- Assumption Parish
- Avoyelles Parish
- Beauregard Parish
- Bienville Parish
- Bossier Parish
- Caddo Parish
- Calcasieu Parish
- Caldwell Parish
- Cameron Parish
- Catahoula Parish
- Claiborne Parish
- Concordia Parish
- De Soto Parish
- East Baton Rouge Parish
- East Carroll Parish
- East Feliciana Parish
- Evangeline Parish
- Franklin Parish
- Grant Parish
- Iberia Parish
- Iberville Parish
- Jackson Parish
- Jefferson Davis Parish
- Jefferson Parish
- Lafayette Parish
- Lafourche Parish
- LaSalle Parish
- Lincoln Parish
- Livingston Parish
- Madison Parish
- Morehouse Parish
- Natchitoches Parish
- Orleans Parish
- Ouachita Parish
- Plaquemines Parish
- Pointe Coupee Parish
- Rapides Parish
- Red River Parish
- Richland Parish
- Sabine Parish
- St. Bernard Parish
- St. Charles Parish
- St. Helena Parish
- St. James Parish
- St. John the Baptist Parish
- St. Landry Parish
- St. Martin Parish
- St. Mary Parish
- St. Tammany Parish
- Tangipahoa Parish
- Tensas Parish
- Terrebonne Parish
- Union Parish
- Vermilion Parish
- Vernon Parish
- Washington Parish
- Webster Parish
- West Baton Rouge Parish
- West Carroll Parish
- West Feliciana Parish
- Winn Parish
Data on this page last rebuilt 30 August 2026. How these figures are produced.