The document that declared the thirteen American colonies independent from British rule is the Declaration of Independence, adopted on July 4, 1776. Authored primarily by Thomas Jefferson, the declaration articulated the colonies' grievances against King George III and justified their quest for freedom. It emphasized fundamental rights, such as life, liberty, and the pursuit of happiness, establishing a foundation for American democracy. This historic document not only signified the birth of the United States but also inspired countless movements for independence and human rights across the globe.