THE ST. MARY'S COUNTY LAND BRIEF
Land in the
Chesapeake Rolling Coastal Plain setting.
St. Mary's County has 358.6 square miles of land in Maryland. 2 mapped landscape regions meet across St. Mary's County: Chesapeake Rolling Coastal Plain, Chesapeake-Pamlico Lowlands and Tidal Marshes.
Irregular plains of sand, silt and clay support a mix of pine and hardwood landscapes. The region has more relief than the lower coastal plain, with generally gentle stream gradients.
Regional context: Southeastern Plains ↗ · Regional mapping across the county footprint
Where the landscape changes
St. Mary's County intersects 2 mapped regional units. The largest mapped shares are:
- Chesapeake Rolling Coastal Plain73.5%
- Chesapeake-Pamlico Lowlands and Tidal Marshes26.5%
Middle Atlantic Coastal Plain in St. Mary's County
Low coastal plains contain terraces, estuaries, marshes and barrier islands. Unconsolidated sediments underlie this varied coastal setting, with forest patterns changing near streams and low-lying areas.
Read the regional source ↗Finding your parcel within St. Mary's County
The atlas lists 11 cities, towns, townships, and Census communities associated with St. Mary's County, including California, Lexington Park, Mechanicsville. The list includes overlapping geography types and does not divide the county into exclusive service areas.
St. Mary's County by land and water
The Census records 405.7 square miles of water within St. Mary's County, or 53.1% of its total area. That share is close to St. Mary's County’s 53.1%. This is geographic context; waterfront status and usable land must be checked at the parcel.
For scale, St. Mary's County has 75.3 times the land area of nearby Callaway CDP (4.76 square miles). These areas describe boundaries, not comparable property prices.
The Census boundary meets Calvert County, Charles County, Dorchester County, Somerset County within Maryland. A tract near one of these lines should be matched to the county identifier on its own records.

