The Bill of Rights was added to the U.S. Constitution primarily to ensure the Constitution's ratification by addressing fears that the new federal government would be too powerful and threaten individual liberties. Many people, especially Anti-Federalists, opposed the Constitution initially because it lacked explicit protections for basic rights that most state constitutions already had. To secure support for the Constitution and prevent calls for a new convention that might undo the work done, key Federalists, including James Madison, agreed to add these ten amendments as a safeguard for personal freedoms and limitations on government power. These amendments, known collectively as the Bill of Rights, were proposed in 1789 and ratified by the states in 1791, providing clear guarantees of rights such as freedom of speech, religion, and the right to a fair trial.