The document that outlined the legal foundation of the United States government is the Constitution, which was ratified in 1788. The Constitution established the framework for the federal government, delineating the powers and responsibilities of each branch: legislative, executive, and judicial. It also included the Bill of Rights, which consists of the first ten amendments that protect individual liberties. The Constitution remains a living document, as it can be amended, ensuring it meets the changing needs and values of the nation. Its principles of democracy and rule of law continue to serve as a foundation for governance in the United States.