Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The United States Constitution has been amended 27 times since the Constitution was ratified in 1788. Far more proposals to amend the country''s supreme law are unsuccessful. Up to 200 amendments are typically proposed in Congress each term. But only 33 such proposals in U.S. history (including the 27 that were ratified) have received the two-thirds vote in Congress necessary to present them to the states. The framers intended that it be difficult to change the Constitution, but not so difficult as to render it an inflexible instrument of government. Their prescription drew upon their experience with the Articles of Confederation, which had been the United States'' previous supreme law since 1781, and which required a unanimous vote of 13 states to amend. This unanimity proved impossible to obtain, and the framers therefore laid out a less stringent process for amending the Constitution in Article V.