The pivotal event that marked the start of the American Revolution against British rule was the Boston Tea Party, which occurred on December 16, 1773. This act of protest against the Tea Act saw American colonists, disguised as Mohawk Indians, dump 342 chests of British tea into Boston Harbor. This rebellion symbolized colonial resistance to British taxation without representation, igniting tensions between the colonies and the British government. The Boston Tea Party rallied support for independence and set the stage for further protests and ultimately the Declaration of Independence in 1776.