By 1900, most of New England had been de-forested, with over 80% of the trees taken for fuel, by farming and by logging. Those "stonewalls" and "stonepiles" now in the woods were often in pastures or cleared lands, and so it was assumed they were all of post-Contact origin, and only in forests now because we've let our forests grow back. This was an incorrect assumption...
There are different forms of possibly ritually significant stonework in New England, what USET (United South & Eastern Tribes) calls Ceremonial Stone Landscapes