Portal:United States/Anniversaries/December/December 21
- 1620 - Plymouth Colony: William Bradford and the Mayflower Pilgrims land on what is now known as Plymouth Rock in Plymouth, Massachusetts.
- 1861 - Medal of Honor: Public Resolution 82, containing a provision for a Navy Medal of Valor, is signed into law by President Abraham Lincoln.
- 1937 - Snow White and the Seven Dwarfs, the world's first full-length animated feature, premieres at the Carthay Circle Theater.
- 1968 - Apollo 8, the first manned mission to the moon, is launched from the Kennedy Space Center in Florida. The crew performs the first ever manned Trans Lunar Injection and become the first humans to leave Earth's gravity.
- 1988 - A bomb explodes on board Pan Am Flight 103 over Lockerbie, Dumfries and Galloway, Scotland, killing 270.