Washington, DC to Harrisburg, PA buses and trains from $45

Or, see buses and trains from Harrisburg, PA to Washington, DC.
Here are some trips other travelers have found on Routefriend.
8h 49m
1 stop
GotoBus GotoBus
3h 55m
1 stop
8h 12m
1 stop
GotoBus Amtrak
9h 10m
1 stop
Vamoose Amtrak