Discovered in Rowan County in 1794, these naturally occurring geological formations were at one point thought to be man-made. The “walls,” which are in a straight line, seem to be “made of stones carefully cut into blocks, fitted and held together by mortar of various colors” (Powell’s Encyclopedia of North Carolina). During the late 18th and early 19th centuries, many individuals speculated that these formations were built by prehistoric inhabitants. By the late 19th century, however, geologists had determined that the formations were “traprock”—formed by magma (made up of basalt, diabase, and gabbro) that had cooled and formed distinctive joints. Scientists also discovered that these “walls” existed in at least a dozen North Carolina counties.
The image above is from the North Carolina Collection’s Photographic Archives (P1-80-N285w). In addition, the Collection has several pages of newspaper clippings regarding the walls and the mystery surrounding them.