Barbara Ann Mikulski (born July 20, 1936) is an American politician and social worker who served as a United States senator from Maryland from 1987 to 2017. A member of the Democratic Party, she also served in the United States House of Representatives from 1977 to 1987. Mikulski is the third-longest-serving female United States Senator, and the longest-serving U.S. Senator in Maryland history.