The historical document that established the principle of popular sovereignty in the United States is the Declaration of Independence. Drafted in 1776, it articulates the idea that government derives its legitimacy from the consent of the governed, asserting that people hold the ultimate authority over their government. This principle emphasizes the importance of individual rights and the ability of citizens to challenge unjust governance. Popular sovereignty became foundational to American democracy, influencing the development of the U.S. Constitution and reinforcing the notion that power rests with the people.