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BWI Thurgood Marshall Airport, a base for Southwest Airlines, is the 22nd busiest airport in the United States and the busiest in the National Capital region. It is named after Thurgood Marshall, a Baltimore native, who was the first African American to serve as an Associate Justice on the U.S. Supreme Court. This airport also draws large numbers of travelers from the Richmond, Harrisburg and Philadelphia metropolitan areas. BWI covers 3,160 acres (1,279 ha) of land.