The abandoned fieldstone walls of New England are every bit as iconic to the region as lobster pots, town greens, sap buckets and fall foliage. They seem to be everywhere—a latticework of dry, lichen-crusted stone ridges separating a patchwork of otherwise moist soils.

Stone walls can be found here and there in other states, but only in New England are they nearly ubiquitous. That’s due to a regionally unique combination of hard crystalline bedrock, glacial soils and farms with patchworks of small land parcels.

Nearly all were built by European settlers and their draft animals, who scuttled glacial stones from agricultural fields and pastures outward to fence lines and boundaries, then tossed or stacked them as lines. Though the oldest walls date to 1607, most were built in the agrarian century between the American Revolution and the cultural shift toward cities and industry after the Civil War.

The mass of stone that farmers moved in that century staggers the mind—an estimated 240,000 miles (400,000 kilometers) of barricades, most stacked thigh-high and similarly wide. That’s long enough to wrap our planet 10 times at the equator, or to reach the moon on its closest approach to Earth.

Natural scientists have been working to quantify this phenomenon, which is larger in volume than the Great Wall of China, Hadrian’s Wall in Britain and the Egyptian pyramids at Giza combined. This work began in 1870 and generated the U.S. government’s 1872 Census of Fences. Today, scientists are using a technique called LiDAR, or light detection and ranging, to measure and map stone walls across New England.