The significant document authored by Thomas Jefferson and adopted in 1776 is the Declaration of Independence. This foundational text proclaimed the thirteen American colonies' separation from British rule, articulating the colonies’ reasons for seeking independence. It expressed Enlightenment ideals, emphasizing unalienable rights such as life, liberty, and the pursuit of happiness. The document criticized King George III for his tyranny and highlighted the colonies' desire for self-governance and democratic principles. The Declaration of Independence served not only to announce independence but also to inspire future movements for freedom and equality, solidifying Jefferson's legacy as a key figure in American history.