Westphalia is a census-designated place in southern Prince George's County, Maryland, United States. The population of the CDP was 11,770 at the 2020 census. The U.S. Census Bureau first defined the Westphalia census-designated place for the 2010 U.S. Census. In the 2020 U.S. Census, portions of Westphalia were given to the new Brown Station …Westphalia is a census-designated place in southern Prince George's County, Maryland, United States. The population of the CDP was 11,770 at the 2020 census. The U.S. Census Bureau first defined the Westphalia census-designated place for the 2010 U.S. Census. In the 2020 U.S. Census, portions of Westphalia were given to the new Brown Station CDP.