The historical document that proclaimed the independence of the American colonies in 1776 is the Declaration of Independence. Drafted by Thomas Jefferson, it outlined the colonies' reasons for seeking separation from British rule, emphasizing principles such as natural rights and the concept of government by consent. Ratified by the Continental Congress on July 4, 1776, the declaration marked a pivotal moment in history, inspiring revolutionary movements worldwide. It not only asserted the colonies' desire for autonomy but also laid the groundwork for the formation of the United States.