Getting in

• Baltimore/Washington International Thurgood Marshall Airport: For Penn Station, take the free airport shuttle to BWI Rail Station, then MARC Penn Line (about 15 minutes; roughly $6) or Amtrak (about $7–35). This is the best choice for Mount Vernon, Station North and Amtrak connections. For the Inner Harbor, the terminal Light Rail is simpler: about 30 minutes, roughly $2. Skip a car rental unless you are leaving the city.
• Baltimore Penn Station: This is the station you want for nearly all intercity rail arrivals: Amtrak Northeast Corridor trains from Washington, Philadelphia, New York and Boston stop here. It is walkable to Station North and Mount Vernon; use the free Purple Charm City Circulator south toward downtown/Federal Hill or take a short rideshare to the harbor rather than changing to the limited Metro Subway.
• Ronald Reagan Washington National Airport: Only use DCA if its airfare is dramatically better. Expect roughly 1½–2 hours door to door: Metro into Washington, then MARC or Amtrak north to Baltimore Penn Station, plus local transfer. BWI is vastly easier.
• Washington Dulles International Airport: A poor Baltimore airport choice unless a nonstop or fare makes it unavoidable. Budget about 2½ hours or more by public transport via Washington and then MARC/Amtrak; a direct car ride can be much longer in weekday traffic.
• Philadelphia International Airport: Viable only when Philadelphia fares work much better. Take SEPTA into Philadelphia, then Amtrak south to Baltimore Penn Station; allow roughly 2½–3 hours door to door. It is not a substitute for BWI on convenience.