The document that declared the thirteen American colonies independent from Great Britain is the Declaration of Independence, adopted on July 4, 1776. Drafted primarily by Thomas Jefferson, it articulates the colonies' grievances against King George III and asserts their right to self-governance. The Declaration emphasizes Enlightenment ideals, including the rights to life, liberty, and the pursuit of happiness. Its adoption marked a significant turning point in American history, as it not only solidified the colonies' break from British rule but also laid the philosophical foundation for the United States as a sovereign nation.