WALK INTO A PATCH OF forest in New England, and chances are you will—almost literally—stumble across a stone wall. Thigh-high, perhaps, it is cobbled together with stones of various shapes and sizes, with splotches of lichen and spongy moss instead of mortar. Most of the stones are what are called “two-handers”—light enough to lift, but not with just one hand. The wall winds down a hill and out of sight. According to Robert Thorson, a landscape geologist at University of Connecticut, these walls are “damn near everywhere” in the forests of rural New England.

He estimates that there are more than 100,000 miles of old, disused stone walls out there, or enough to circle the globe four times.

Who would build a stone wall, let alone hundreds of thousands of miles of them, in the middle of the forest?

https://www.atlasobscura.com/articles/new-england-stone-walls