St. Mary's County GIS Maps

St. Mary's 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's County Parcels

St. Mary's County has 50,663 mapped parcels covering 229,790 acres. The median assessed value is $338,200. The median lot size is 0.77 acres. 3,375 parcels are 10 acres or larger. Residential accounts for 75.5% of parcels. Town houses follow at 6.5% and agricultural at 5.8%. Of the parcels with a recorded build year, half were built in 1992 or earlier. The records carry 41,591 distinct owner names. About 6% of parcels list an owner mailing address outside Maryland. Owner names, mailing addresses and lot sizes are on nearly every parcel. Site addresses reach 86.5%. Assessed values reach 97.6%. Browse the interactive St. Mary's County Parcel viewer here.

St. Mary's County Parcel Data Coverage

Field coverage measured across all St. Mary's County parcel records. Download free sample data here.

St. Mary's County Population

St. Mary's County had 113,777 residents in 2020. That was 8.2% higher than in 2010. St. Mary's County added 27,566 people between 2000 and 2020, which points to steady long-term growth. The county is fairly spread out, with about 317 people per square mile. Some of the county's most populated postal areas include Lexington Park, Mechanicsville and Leonardtown.

Population Trend in St. Mary's County MD

St. Mary's County Population per 2000, 2010 and 2020 census counts with a baseline 2030 projection.

St. Mary's County Zip Codes

St. Mary's County has 26 zip codes. Some of the county's most populated zip codes include Lexington Park (20653), Mechanicsville (20659) and Leonardtown (20650). Lexington Park is the largest zip by population, with about 25,180 residents or 22% of the county total. Together, the three largest zips account for about 57% of all county residents based on 2020 population estimates.

Most Populated Zip Codes in St. Mary's County MD

St. Mary's County Zip Code populations and trends per most recent census data.

St. Mary's County Demographics

St. Mary's County has a median age of 37, which makes the county a little younger than Maryland overall. About 24% of residents are under 18, while 13.7% 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 33.5% of the population, which points to a solid working-age base. About 35.1% of adults have a bachelor's degree or higher, above the statewide figure of 42.7%. The county is majority White by population, with Hispanic, Asian, Black and multiracial residents making up a meaningful share of the local mix.

Key Demographics for St. Mary's County MD

St. Mary's County School Districts

St. Mary's County is served by 1 public school district with 16,905 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's County MD

St. Mary's County school district enrollment and trends per most recent NCES reporting data.

St. Mary's County Housing & Real Estate

St. Mary's County has a median home value of $390,900 and a median gross rent of $1,692. About 73% of occupied homes in the county are owner-occupied, so the local housing market leans heavily toward ownership. Home values run below the Maryland median, while rents come in above the state average. In March 2026, the median listing price was $462,400 and homes spent about 23 days on the market.

Businesses in St. Mary's County, MD

St. Mary's County has 3,739 business listings across 612 categories. The largest categories in St. Mary's County business listings are Real Estate Agents (92, 2.5%), Churches & Religious Organizations (81, 2.2%), and Auto Repair (61, 1.6%). The full St. Mary's County business listings dataset includes names, categories, addresses and contact details where available. St. Mary's 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's County, MD

St. Mary's County Business Listings

St. Mary's County business listings sourced from Overture Maps. Includes locations with a high level of confidence.

Preview a Live Package Demo

See exactly what is included in a county data package. Inspect how files are organized, the interactive data explorer and how maps and analytics are laid out. The demo loads a real sample package from Maryland — explore the full structure before you buy.