You can get from the Baltimore/Washington International Thurgood Marshall Airport to Washington, D.C. though a variety of ways including driving on the Baltimore-Washington Parkway. Other options are taking an Amtrak train from the airport to Washington, D.C. or using the MARC train service.
As of 2015, driving to Washington, D.C. from BWI takes an estimated 56 minutes according to directions from Google Maps; the route covers 32.8 miles. Take an Amtrak train from BWI to Washington, D.C. in as little as 1 hour, 35 minutes according to the Amtrack.com website.
The Penn Line on the MARC train line services riders from BWI Airport to Union Station in Washington, D.C., according to the MTA MARC Train Schedule and Maps page of the Transportation Resource Information Point website.