St. Mary County GIS Maps
St. Mary County, Louisiana, has 49,406 residents and covers 555.6 square miles. The population declined 9.6% between the 2010 and 2020 census. More residents left than arrived over that decade. The FIPS code for St. Mary County is 22101.
Morgan City is the county's largest population center. St. Mary County also includes 8 zip codes, 1 public school district and 14 municipalities. Those boundaries help explain why population, schools, and housing can look different from one part of the county to another. The map below shows how those county lines, zip codes, and school districts fit together, and the sections that follow use that same geography to show population, demographics, school enrollment and housing patterns in more detail.
Maps, GIS layers and sample data. Paid packages add full layers, analytics and database files.
St. Mary County Trends
- Population
- 49,406▾
- Median Home Value
- $128,000—
- K-12 Enrollment
- 7,153▾
County analytics dashboards with historical trends & projections included in package downloads.
Free starter access previews county maps, lightweight GIS, and sample data. Paid packages unlock full GIS layers, analytics, and database files.
St. Mary County Maps
The maps below show a few of the county map styles included in our downloads. County packages include map exports in JPEG, PNG, SVG, PDF and GeoTIFF formats plus more than 20 GIS layers for mapping, research and analysis. Available layers include zip codes, area codes, subdivisions, school districts, political boundaries, roads, water features, points of interest and more.
County packages also include historical county demographics, business intelligence, analytical dashboards, AI-ready prompts, markdown files and related reference data. Everything is organized to save hours of manual work collecting current data, cleaning it and joining it together. That makes it easier to move faster on analytics, due diligence, business planning and location research. Paid packages are built for commercial use, but some package contents include source-specific attribution or notice guidance. Review Licensing & Data Source Notices.
St. Mary County Population
St. Mary County had 49,406 residents in 2020. That was 9.6% lower than in 2010. St. Mary County had 4,094 fewer people in 2020 than it did in 2000, which points to a long-term population decline. The county is fairly spread out, with about 89 people per square mile. Some of the county's most populated postal areas include Morgan City, Franklin and Patterson.
Population Trend in St. Mary County LA
St. Mary County Population per 2000, 2010 and 2020 census counts with a baseline 2030 projection.
St. Mary County Zip Codes
St. Mary County has 8 zip codes. Some of the county's most populated zip codes include Morgan City (70380), Franklin (70538) and Patterson (70392). Morgan City is the largest zip by population, with about 21,079 residents or 43% of the county total. Together, the three largest zips account for about 85% of all county residents based on 2020 population estimates.
Most Populated Zip Codes in St. Mary County LA
| ZIP | Area | Population | Trend |
|---|---|---|---|
| 70380 | Morgan City | 21,079 | ▾ -8.1% |
| 70538 | Franklin | 12,604 | ▾ -15.1% |
| 70392 | Patterson | 8,406 | ▾ -0.6% |
| 70342 | Berwick | 4,806 | ▾ -3.5% |
| 70514 | Baldwin | 1,843 | ▾ -27.6% |
| Download all zip code data | |||
St. Mary County Zip Code populations and trends per most recent census data.
St. Mary County Demographics
St. Mary County has a median age of 39.7, which makes the county a little older than Louisiana overall. About 24.4% of residents are under 18, while 18% are 65 or older. That gives the county a fairly even mix of younger families and older adults. The largest age group is 25 to 44 at about 29.2% of the population, which points to a solid working-age base. About 13.1% of adults have a bachelor's degree or higher, above the statewide figure of 26.6%. The county has a more diverse population mix, with no single race or ethnicity accounting for all of the local story.
Key Demographics for St. Mary County LA
Median Age
39.7
Under 18
24.4%
Age 65+
18%
Bachelor's+
13.1%
St. Mary County School Districts
St. Mary County is served by 1 public school district with 7,153 students enrolled in 2024. Several larger districts account for a substantial share of students across the county map area. Those three districts account for about 100% of public school enrollment in the map area. Total enrollment has stayed fairly steady in recent years, but it is slightly lower than it was in 2017.
Largest School Districts by Enrollment in St. Mary County LA
| District | Enrollment | Share | Trend |
|---|---|---|---|
| St. Mary Parish School District | 7,153 | 100% | ▾ -8.2% |
| Download all school district data | |||
St. Mary County school district enrollment and trends per most recent NCES reporting data.
St. Mary County Housing & Real Estate
St. Mary County has a median home value of $128,000 and a median gross rent of $839. About 70% of occupied homes in the county are owner-occupied, so the local housing market leans heavily toward ownership. Home values run below the Louisiana median, while rents come in below the state average. In March 2026, the median listing price was $185,000 and homes spent about 129 days on the market.
St. Mary County Housing Mix
St. Mary County housing mix: owner, renter and vacant units.
St. Mary County Housing Trends
St. Mary County median home value and rent trend (last 5 years).
Businesses in St. Mary County, LA
St. Mary County has 1,975 business listings across 454 categories. The largest categories in St. Mary County business listings are Churches & Religious Organizations (69, 3.5%), Baptist Church (35, 1.8%), and Auto Repair (35, 1.8%). The full St. Mary County business listings dataset includes names, categories, addresses and contact details where available. St. Mary County packages also include U.S. Census County Business Patterns data with establishment counts, employment and payroll by industry sector.
Top Business Categories in St. Mary County, LA
| Category | Businesses | Share |
|---|---|---|
| Churches & Religious Organizations | 69 | 3.5% |
| Baptist Church | 35 | 1.8% |
| Auto Repair | 35 | 1.8% |
| Beauty Salons | 31 | 1.6% |
| Convenience Stores | 30 | 1.5% |
| Gas Stations | 29 | 1.5% |
| Bars & Nightlife | 25 | 1.3% |
| Contractors | 23 | 1.2% |
| Discount Store | 23 | 1.2% |
| Professional Services | 22 | 1.1% |
St. Mary County Business Listings
| Business | Category | City |
|---|---|---|
| Fairview Treatment Center | Abuse And Addiction Treatment | Morgan City |
| Vickie's Pier | Accommodation | Franklin |
| Darnall Sikes Gardes | Accountant | Morgan City |
| Martin's Louisiana Alligator Hunts | Active Life | Franklin |
| Mabels Kitchen | Adult Entertainment | Charenton |
| Action Advertising | Advertising Agency | Morgan City |
| Perry's Flying Center | Airport Terminal | Patterson |
| Rebos Club | Alcohol And Drug Treatment Centers | Morgan City |
| Southern ENT Associates Morgan City LA | Allergist | Morgan City |
| Acadian Ambulance Service | Ambulance And Ems Services | Morgan City |
| Download St. Mary County business listings | ||
St. Mary County business listings sourced from Overture Maps. Includes locations with a high level of confidence.
Get the Full St. Mary County Data Package
This page shows a preview of what's included in the St. Mary County data package. The full package gives you a ready-to-use county data system with GIS layers, historical data, maps, database files and planning tools that save hours of manual data gathering, cleanup and joins. Everything is organized to help you skip data wrangling and start analysis faster.
- 20+ GIS layers for zip codes, school districts, roads, water, boundaries and more
- Historical county demographics, housing, income and trend data
- ZIP code population files and school district enrollment history
- Database files, markdowns, AI-ready prompts and documentation
- Map exports in PNG, JPEG, PDF, SVG and GeoTIFF formats
- Offline-ready data explorer, map and analytics tools
Paid packages support commercial use, client work, and derived outputs. Some package contents may include source-specific attribution or provider notices. See Licensing & Data Source Notices.
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Nearby Counties
Browse county data pages for the counties that border St. Mary County. These nearby pages include the same mix of county maps, demographic summaries, school district context, housing trends and package links.