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St. Mary's County MDGenWeb is a free genealogical site about the history of the county. We hope you find helpful clues for your research of St. Mary's county ancestors.

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County Coordinator: You? St. Mary's County MDGenWeb is Available for Adoption.

Temporary County Coordinator: Norma Hass normahass01@gmail.com

COUNTY FORMATION

St. Mary's County was established in 1637. It was one of eight original counties of the State of Maryland. Located in the southern part of the state, the Potomac River delineates St. Mary County's southern border, separating it from Westmoreland and Northumberland Counties, Virginia. Although water rights are still disputed, St. Mary's County waters are also bordered by Virginia's territorial waters in Potomac tributary mouths on the Virginia side, tidal interface zones, and the Chesapeake Bay. Dorchester County, lies across the water to the east. Charles County is to the west, and Calvert County is north of St. Mary's County.

In 1696, St. Mary's County gained additional territory from Calvert County, pushing its boundary line further north.

Leonardtown is the county seat.