Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more . CNN  —  The oldest known surviving tombstone in the United States is an elaborate display of wealth — an intricately carved slab of black limestone initially laid in the floor of the second church of Jamestown, Virginia, the first permanent British settlement in North America. Often referred to as the “Knight’s Tombstone” due to the carvings of a