Enslaved people used codes to mark graves on plantation grounds.
IN MODERN-DAY ALTAVISTA, VIRGINIA, A town that covers 5 square miles of what was the first English colony in North America, sits the Avoca Museum. The former residence of Colonel Charles Lynch, a politician and American Revolutionary Patriot, it was built in 1901 and is now a Virginia Historic Landmark. Beyond the stately home, whose porch and eaves are marked by flourishes derived from the British-born Queen Anne style, is a dirt clearing within a patch of aged oak trees. Upon closer look, there’s a constellation of irregularly shaped rocks placed with curious precision—some squat, some narrow.