Great Mills is an unincorporated community

Unincorporated area

In law, an unincorporated area is a region of land that is not a part of any municipality.To "incorporate" in this context means to form a municipal corporation, a city, town, or village with its own government. An unincorporated community is usually not subject to or taxed by a municipal government...

 in St. Mary's County, Maryland

Maryland

Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...

, United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. Great Mills High School serves the lower end of the county, including the town (census CDP) of Lexington Park

Lexington Park, Maryland

Lexington Park is a census-designated place in St. Mary's County, Maryland, United States, and the principal community of the Lexington Park, Maryland Micropolitan Statistical Area...

; there is a public swimming pool adjacent. Great Mills Road, connecting the community with Lexington Park, has small shopping centers and small, low to middle-income housing developments.