Maryland

Buying Land in St. Mary's County, Maryland

Seat Leonardtown. St. Mary's is where Maryland's colonial story began in 1634, and it's also home to Naval Air Station Patuxent River, a major active Navy flight-test installation whose Air Installation Compatible Use Zone program shapes what nearby land is realistically suited for. The county still runs a traditional Board of County Commissioners, one of a shrinking number left in Maryland.

NAS Patuxent River: Real Noise and Accident-Potential Zone Exposure

Case-by-case / verify locally

Naval Air Station Patuxent River operates under a formal Air Installation Compatible Use Zone (AICUZ) program (established 1978) that defines Accident Potential Zones and high-noise contours extending into surrounding St. Mary's County land. County Commissioners and base officials hold regular joint meetings on these encroachment issues, including a proposed AICUZ disclosure statement for residential leases. See our dedicated standalone on NAS Patuxent River's AICUZ zones for what to check before buying land near the base.

Maryland's First Capital: St. Mary's City, Founded 1634

Case-by-case / verify locally

St. Mary's City, founded in March 1634, was Maryland's first colonial capital until 1694 and is now a National Historic Landmark and state-run living-history site. This is a genuine, well-documented historical distinction, though the historic area itself is a state museum property, not a source of buildable private land.

Traditional Board of County Commissioners Since 1838

Generally favorable

St. Mary's has used the traditional county commissioner form of government since 1838 and remains one of a shrinking number of Maryland counties still using it -- voters have rejected full charter government at least twice. Combined legislative and executive authority sits with the Commissioners rather than a separately elected County Executive.

Naval Air Station Patuxent River: a genuine land-use compatibility factor

Naval Air Station Patuxent River, headquarters of the Navy's flight test and evaluation programs, occupies a large peninsula in southern St. Mary's County and is one of the county's most significant economic anchors. But its role in local land-use planning goes well beyond economics: the base operates under a formal Air Installation Compatible Use Zones (AICUZ) program, first established in 1978, which maps Accident Potential Zones (APZs) around runway approach and departure paths and defines noise contours -- documented in current joint-meeting materials as reaching roughly 65 decibels at the APZ Zone II contour and extending into other parts of the county beyond the installation's own boundary.

St. Mary's County Commissioners and NAS Patuxent River's Commanding Officer hold regular joint meetings specifically to address encroachment issues, including recent discussion of a proposed AICUZ disclosure statement that would be provided to residential leases in affected areas -- a formal acknowledgment that the county and the Navy both treat this as an active, ongoing land-use planning concern rather than a historical footnote. For a buyer considering land anywhere near the base, this is worth taking seriously: see our dedicated standalone on NAS Patuxent River's AICUZ zones for the specifics of what to check.

Where Maryland began: St. Mary's City, 1634

St. Mary's County holds a distinction no other Maryland jurisdiction can claim: it's where the colony itself began. In March 1634, colonists led by Leonard Calvert, who had sailed from England aboard the Ark and the Dove, established St. Mary's City on a bluff above the tidal St. Mary's River near the mouth of the Potomac. The settlement served as Maryland's colonial capital from 1634 until 1694, when the seat of government moved to Annapolis, and it is recognized today as the fourth-oldest permanent English settlement in the present-day United States.

Historic St. Mary's City is now a National Historic Landmark and a state-run living-history museum and archaeological site, reconstructing elements of the original colonial settlement. For a land buyer, this matters mostly as context rather than a direct due-diligence item: the historic area itself is state-owned museum property, not private land available for purchase, but the surrounding southern St. Mary's County landscape -- much of it still rural and agricultural -- carries this history as part of what makes the county a genuinely distinctive part of Maryland beyond its Navy-town reputation.

Government structure, Critical Area, and septic/well basics

St. Mary's has operated under the traditional county commissioner form of government since 1838, and remains one of a shrinking number of Maryland counties still using that model rather than a charter or code-home-rule structure. Voters have rejected a move to full charter government on at least two occasions; the Commissioners hold combined legislative and executive authority for the county, including final say on zoning ordinances within whatever authority the state legislature has delegated to a commissioner-form county.

St. Mary's peninsula geography, bounded by the Potomac River, the Patuxent River, and the Chesapeake Bay, places it among the roughly 16 Maryland counties administering a certified Critical Area program under the state's 1984 Critical Area Act described on our Maryland state page. Septic and well permitting follow the same statewide COMAR 26.04.02 and 26.04.04 standards used throughout Maryland, run locally by the St. Mary's County Health Department -- and given the county's extensive tidal shoreline, the state's Bay Restoration Fund for nitrogen-reducing septic upgrades is worth asking about for any parcel with an existing older system near the water.

What we could and couldn't confirm

St. Mary's County's FIPS code (24037) is drawn from this project's own Maryland ledger, which alphabetizes the county under "Saint Mary's" for FIPS-sequence purposes, placing it before Somerset County (24039). The 1838 commissioner-government start date and the two-occasions charter-rejection history come from Conduit Street/Maryland Association of Counties reporting; this page did not independently confirm whether the county has since formally adopted code home rule as of the current date, so it describes the county as continuing to use the traditional commissioner form based on the most recent sourcing found. The St. Mary's City founding date (1634) and its status as the fourth-oldest permanent English settlement in the present-day US are corroborated across Britannica and Wikipedia. The AICUZ program's 1978 establishment date and the ~65-decibel APZ Zone II noise-contour figure come from St. Mary's County's own 2025 joint-meeting press release and somdnews.com reporting. St. Mary's inclusion among Maryland's roughly 16 Critical Area counties is drawn from a WebSearch-derived synthesis rather than a primary Maryland Department of Planning jurisdiction list. Direct WebFetch to stmaryscountymd.gov was not attempted; findings otherwise rely on WebSearch-indexed content.

Verify directly with: the St. Mary's County Department of Land Use and Growth Management for zoning and Critical Area status on a specific parcel, NAS Patuxent River's public affairs office for current AICUZ zone maps, and the county Health Department for septic/well permitting

Who to Call Before Buying Land in St. Mary's County

Direct WebFetch to stmaryscountymd.gov was not attempted in this research pass, so current department structure, fees, and turnaround times should be confirmed directly. NAS Patuxent River itself is federal property administered by the U.S. Navy, not by any county office listed here, though the county and the base coordinate directly on AICUZ-related land-use issues.

Planning & Zoning