The critical document that served as the basis for United States law is the Constitution, ratified in 1788. This foundational document established the framework of the U.S. government, delineating the powers and responsibilities of its three branches: legislative, executive, and judicial. It embodies the principles of democracy, including checks and balances, separation of powers, and individual rights through the Bill of Rights, adopted in 1791. The Constitution has been amended multiple times to reflect the evolving values and norms of American society, serving as a living document that guides legal interpretations and governance, influencing international law and constitutional frameworks globally.