Once you've seen one stone wall you've seen every stone wall. I suppose it doesn't really matter because the Northeast government doesn't have any "public" land anymore anyway.
A stone wall is more than just some historical oddity or trinket: its function is embedded within the landscape. Stone walls lose their meaning without a spatial context. The state has the responsibility to act to preserve this element of the Northeast's cultural heritage because each wall, since it is located at a unique place, has historical value.