The Bill of Rights is critical in the U.S. Constitution as it enumerates the first ten amendments that guarantee individual liberties and rights. Established in 1791, it protects freedoms such as speech, religion, and assembly, ensuring that the government cannot infringe upon these rights. The Bill of Rights serves as a safeguard against tyranny and plays a vital role in defining the relationship between citizens and the state. It also influences legal interpretations and serves as a foundation for further civil liberties advancements in American history.