Since 1937, the United States' Tomb of the Unknown Soldier at Arlington Cemetery has been guarded by soldiers every minute of every day. The tomb is in honor of those who died in war and whose bodies were never identified. The guards' movements are steep in tradition and meant to represent a 21-gun salute, which is one of the United States military's greatest honors. They only take 21 steps and pause for 21 seconds before making their next movement.