The Bill of Rights is the name for the first ten amendments to the United States Constitution, which limit the power of the federal government and guarantee citizens of the United States certain rights. The amendments were written in 1789 by James Madison, and were based on important ideas about personal rights. The Bill of Rights went into effect in 1791, when 3/4 of the states agreed that they were fair. Originally, the Bill of Rights had 12 different amendments, but the first two were not passed by enough states. The second amendment that was not passed was eventually added to the Constitution in 1992, becoming the 27th amendment in the Constitution.