Southern Maryland, also referred to as SoMD, is a geographical, cultural and historic region, as well as a National Heritage Area, in Maryland composed of the state's southernmost counties on the Western Shore of the Chesapeake Bay. According to the state of Maryland, the region includes all of Calvert, Charles, and St. Mary's counties and the sout…Southern Maryland, also referred to as SoMD, is a geographical, cultural and historic region, as well as a National Heritage Area, in Maryland composed of the state's southernmost counties on the Western Shore of the Chesapeake Bay. According to the state of Maryland, the region includes all of Calvert, Charles, and St. Mary's counties and the southern portions of Anne Arundel and Prince George's counties. It is largely coterminous with the region of Maryland that is part of the Washington metropolitan area. Portions of the region are also part of the Baltimore Metropolitan Area and the California-Lexington Park Metropolitan Statistical Area. As of the 2020 Census, the region had a population of 373,177. The largest community in Southern Maryland is Waldorf, with a population of 81,410 as of the 2020 Census.