Barnard College to American University buses and trains from $35

Or, see buses and trains from American University to Barnard College.
Here are some trips other travelers have found on Routefriend.
4h 21m
1 stop
Metro-North GotoBus
5h 21m
1 stop
Metro-North Vamoose
5h 4m
1 stop
Metro-North Amtrak
5h 22m
2 stops
Metro-North Amtrak