Visit any of the approximately 150 national military cemeteries in the United States

and collectively you will find nearly 1,000,000 headstones marking the final resting place of U.S. Military personnel killed in battles beginning with the Civil War to the present. Spend an extra few minutes reading the names on the headstones, and you will find representatives of every ethnic, religious, geographic, and societal group existing in America today. Their names, dates of birth and death, their military rank and last unit, and their home state are clearly carved in stone.

That’s only half the story. Lift your eyes, look around, and you will see other identical headstones—identical in shape and size but different in that these stones bear no name except Unknown.