GREAT SONG WITH GREAT MESSAGE

I happened on a TV accounting of Johnny Cash's life this afternoon.  One song really registered with me.  For some reason, I don't recall ever hearing it before.  I guess it wasn't all that popular.  Wonder why?

I just had to go to YouTube and look it up.  Here's the link so you can listen to it also:  http://www.youtube.com/watch?v=iXRmJyIyJbM.