The document that established the independence of the United States from British rule is the Declaration of Independence. Adopted on July 4, 1776, it was primarily drafted by Thomas Jefferson and outlined the colonies' grievances against King George III. The Declaration proclaimed the colonies' right to be free and independent states, asserting fundamental principles of individual rights and government by consent. This historic document not only facilitated the break from British governance but also inspired democratic movements around the globe, solidifying the ideals of liberty, equality, and the pursuit of happiness.