James Madison suggested the Bill of Rights in 1789. He realized that many people felt the new Constitution was not strong enough without some statements about individual rights. The Bill of Rights added the first ten amendments to the Constitution and became effective December 15, 1791. Children could read a kid-friendly version of the rights: http://constitutioncenter.org/media/files/CK130001_CivicsKids-2013-PAGES-FNL-Lesson3.pdf
National Archives and Records Administration (NARA) was created in 1934. It centralizes federal documents and makes them available to the public. The National Archives Building in Washington, DC, houses originals of the Declaration of Independence, the Constitution, and the Bill of Rights. One of the four copies of the Magna Carta is also there. Children can visit the National Archives website at: http://www.nara.gov.
United States Constitution became the law in 1788. New Hampshire became the ninth state to ratify the Constitution, and plans were put into action to have the document become the law of the land. Children can learn more at: http://www.congressforkids.net/Constitution_delegates.htm.