If you are driving thru New England and pull over to any forest you can start walking and eventually you will find a short stone wall. These stone walls used to mark the borders of farm land but now they are in the middle of the forest. They are everywhere! Really gives you an idea of how much farming used to go on there.
Of course, that is anecdotal, you can read more here: https://www.bostonglobe.com/metro/2013/08/31/new-england-see...