The U.S. document that enumerates the rights of citizens and limits governmental power is the Bill of Rights. Ratified in 1791 as the first ten amendments to the Constitution, the Bill of Rights guarantees fundamental freedoms, including speech, religion, and assembly. It serves as a crucial safeguard against government overreach, ensuring that individual liberties are protected from infringement. The Bill of Rights exemplifies the principles of democracy and accountability, reinforcing the importance of individual rights in American governance.