Referring to the question of piles of rocks from the amature, In my experience
it was very common for piles of rock to be a result of historic field clearing.
It is common in Kentucky, I am sure.  I am not sure about other areas.  There
is the possibility that these rock piles may be prehistoric stone mounds,
however, I do not have much experience in that department.  The description
sounds more like land clearing to me.  Hope I have helped.
 
 
      M. Jay Stottman
      University of Kentucky