George Mason, a largely forgotten founding father, is really the person behind why we have a Bill of Rights today.
Mason wrote Virginia’s Bill of Rights, and while he was present at the Constitutional Convention, refused to sign it along with Edmund Randolph and Elbridge Gerry because of the lack of a Bill of Rights. Mason had proposed a Bill of Rights, but Federalists argued that because of certain rights already retained by the Constitution and the fact that states had their own bills of rights, there was no need for a national Bill of Rights.
While he was initially opposed to the idea, Madison eventually came around to the concession and drafted initially 12 amendments to be proposed. These were heavily influenced by Mason’s Virginia Bill of Rights. On December 15 1791 the first 10 were added to the Constitution.