Thirty-three amendments to the United States Constitution have been proposed by the United States Congress and sent to the states for ratification since the Constitution was put into operation on March 4, 1789. Twenty-seven of these, having been ratified by the requisite number of states, are part of the Constitution. The first ten amendments were adopted and ratified simultaneously and are known collectively as the Bill of Rights. Six amendments adopted by Congress and sent to the states have not been ratified by the required number of states. Four of these amendments are still technically open and pending, one is closed and has failed by its own terms, and one is closed and has failed by the terms of the resolution proposing it.
Article Five of the United States Constitution details the two-step process for amending the nation's frame of government. Amendments must be properly Proposed and Ratified before becoming operative. This process was designed to strike a balance between the excesses of constant change and inflexibility.
Approximately 11,699 proposals to amend the Constitution have been introduced in Congress since 1789 (as of January 2017). Collectively, members of the House and Senate typically propose around 200 amendments during each two–year term of Congress. Most, however, never get out of the Congressional committees in which they were proposed, and only a fraction of those that do receive enough support to win Congressional approval to go through the constitutional ratification process. Beginning in the early 20th century, Congress has usually, but not always, stipulated that an amendment must be ratified by the required number of states within seven years from the date of its submission to the states in order to become part of the Constitution. Congress' authority to set ratification deadline was affirmed by the United States Supreme Court in Coleman v. Miller, 307 U.S. 433 (1939).
The thirty-three amendments to the United States Constitution—both ratified and unratified—are listed and detailed in the tables below.