December 16 is Boston Tea Party Day. It commemorates the 1773 protest where American colonists dumped British tea into Boston Harbor to protest unfair taxation.
This was a key event leading to the American Revolution and it is remembered annually with reenactments and commemorative events.
On December 16, 1773 memebers of a group called the Sons of Liberty, disguised themselves as Native Americans and boarded three ships in Boston Harbor. They destroyed 342 chests of tea by tearing them open and dumping them into the harbor. This was a protest of the Tea Act and "taxation without representation" from the British Parliament.
The already tense situation was met with the punitive Intolerable Acts and the colonists became united against England sparking the American Revolution.