- Congress approved a resolution in 1921 for a memorial at Arlington honoring unidentifiable soldiers killed in battle. The first guards of the tomb were civilians. The first military guards began watch in 1926. The 3rd U.S. Infantry Regiment took over in 1948. The regiment is the oldest active duty regiment in the Army, and is referred to as "The Old Guard."
- The pace of the tomb guards has numerical significance. The number 21 is considered a high honor in the military, which is the reason for the 21-gun salute. During his watch, the guard walks 21 paces on the walkway beside the tomb. He faces the tomb for 21 seconds as a gesture of respect, turns, and stops for 21 more seconds before walking 21 paces back across the walkway.
- All guards have volunteered for the post. To be considered for admission, males must be at least 5 feet, 10 inches tall. Females must be at least 5 feet, 8 inches tall. Candidates must be U.S. citizens. All guards must successfully pass a two-week training course, which includes learning seven pages of history about the Arlington Cemetery and being able to recite it verbatim. Candidates must pass several tests. Even after being selected, a guard must serve for nine months before he can wear the honor guard silver medal. The medal is a wreath design with an image of the tomb and two figures representing victory and valor.
- The changing of the guards takes place every hour in the fall and winter and every half-hour in the spring and summer. The changing ceremony begins with a relief commander walking to the tomb to salute it, then announcing that spectactors should stand and be quiet during the ceremony. The commander then inspects the new guard's weapon, an M-14 rifle. Commander and new guard then meet the retiring guard on the tomb walkway. After all three salute the tomb, the officer issues the commands for the retiring officer to leave and the new guard to take position.