Here are some of the great American train stations, east coast and west.  They include Union Station Washington DC, Union Terminal Cincinnati. Grand Central Terminal New York  and Union Station Los Angeles.  These are stations that still exist built in the early twentieth century as  Beaux Arts as well as Art Deco style.  Also  Union Station Buffalo which still exists, though is now longer used as a train station.  They show an example of great buildings that have the ability to change function.