Article Five of the United States Constitution
Almost right away, the amendments process became very important.  North Carolina and Rhode Island refused to ratify the Constitution without a Bill of Rights.  This meant they would not be a part of the new United States Government.  In 1789, James Madison wrote the Bill of Rights.  They were ratified together, as the first ten amendments to the Constitution, in 1791.  Having a Bill of Rights convinced North Carolina and Rhode Island to ratify the Constitution.