The document that established the boundaries and governance of the United States in 1789 is the United States Constitution. It provided the framework for the federal government, delineating the powers of each branch and establishing the rule of law. Ratified in 1788, it replaced the Articles of Confederation and was designed to ensure a stronger central government while protecting individual rights. The Bill of Rights, added in 1791, further guaranteed citizens' liberties and limited government powers. This foundational document has endured as a symbol of democracy and has been amended multiple times to reflect the evolving values of American society.