St. Mary's County occupies the southern tip of Maryland's Western Shore peninsula — bounded by the Potomac River on the west, the Chesapeake Bay on the east, and the Patuxent River on the north. The county is dominated by Naval Air Station Patuxent River (Pax River) and the Navy's associated research, test, and evaluation mission, with the resulting civilian defense-contractor workforce shaping the Lexington Park / California commercial corridor. The permit environment combines the Maryland Building Performance Standards, extensive Chesapeake Bay Critical Area along the county's 400+ miles of tidal shoreline, and substantial AICUZ overlay from Pax River operations.
The county's consolidated Department of Land Use and Growth Management (LUGM) administers:
Discretionary review runs through the Planning Commission (advisory) and the Board of County Commissioners (decision).
St. Mary's Comprehensive Plan uses a development district / residential district / rural preservation structure:
Growth is directed to the Development Districts. Subdivision in Rural Preservation areas faces tight density and infrastructure constraints.
Naval Air Station Patuxent River is the Navy's premier aviation research, test, and evaluation base. Pax River operations include F-35 test and evaluation, P-8 Poseidon, MH-60 Seahawk, and unmanned systems research — producing substantial aviation activity and associated noise.
The AICUZ overlay covers:
St. Mary's has incorporated AICUZ provisions into its zoning ordinance, restricting residential and assembly uses in higher-noise contours. Pax River's presence also drives:
St. Mary's 400+ miles of tidal shoreline on the Potomac, Patuxent, St. Mary's River, Breton Bay, and the Chesapeake Bay itself place nearly all waterfront parcels within the 1,000-foot Critical Area overlay. IDA / LDA / RCA classifications apply, with Critical Area Commission oversight on modifications.
See our Maryland Critical Area essay.
Waterfront projects typically face significant Critical Area constraints — impervious area limits, 100-foot building setback from tidal waters, and density restrictions in LDA / RCA classifications.
St. Mary's City — Maryland's first capital (1634) — is both a National Historic Landmark and an archaeological site administered by the state through the Historic St. Mary's City Commission. Projects in or adjacent to the site require coordination with the Commission and with Maryland SHPO for federal-nexus projects.
Other historic resources include the Sotterley Plantation, various waterfront villages (Solomons Island in adjacent Calvert County shares some regional planning), and the 1676 St. Mary's City brick chapel reconstruction.
The Metropolitan Commission (METCOM) provides water and sewer in the Lexington Park / California service area and growth districts. Rural areas use private wells and septic.
Roads are state-maintained (SHA) for principal corridors (Route 5 / Point Lookout Road, Route 235 / Three Notch Road, Route 245). The county maintains some local roads. The Patuxent River Naval Air Station maintains its own internal road network behind the security perimeter.
Three practical rules for St. Mary's:
St. Mary's southern-Maryland rural-meets-defense-industrial character produces a permit environment where the MBPS provides baseline technical uniformity but AICUZ and Critical Area overlays substantially shape development patterns.
Primary sources for this essay: St. Mary's County Code (Zoning Ordinance, Subdivision Regulations); Maryland Building Performance Standards; Chesapeake Bay Critical Area Act (NR Article § 8-1801 et seq.) and local implementing ordinance; Patuxent River Naval Air Station AICUZ Study; St. Mary's Comprehensive Plan; Maryland Forest Conservation Act; METCOM service rules. LUGM, Historic St. Mary's City Commission, METCOM, and MD SHA are the agency resources.