Final answer:
The Bill of Rights was added to the U.S. Constitution in 1791 to protect individual liberties. It was introduced to Congress by James Madison and became the first ten amendments to the Constitution.
Step-by-step explanation:
The Bill of Rights was added to the U.S. Constitution in 1791. It was added because the new Constitution created a powerful federal government, which caused concerns among many people who feared that their rights would be deprived. To allay these concerns, the framers promised that a Bill of Rights safeguarding individual liberties would be added. Virginia Representative James Madison introduced the Bill of Rights to Congress in 1789, and it was formally adopted in 1791 as the first ten amendments to the Constitution.