The Southern Maryland Region (or Tri-County Region) is comprised of three counties:
Calvert, Charles and St. Mary's.
 The Calvert County seat is Prince Frederick.
 The Charles County seat is La Plata
 The St. Mary's County seat is Leonardtown
There are six incorporated towns located within the region, they include:
 Chesapeake Beach (Calvert)
 Indian Head (Charles)
 La Plata (Charles)
 Leonardtown (St. Mary's)
 North Beach (Calvert)
Village of Port Tobacco (Charles)
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