Article VII of the U.S. Constitution required nine state ratifications for the Constitution to take effect.
The article specified that approval by conventions in nine of the thirteen states would be sufficient to establish the Constitution among the ratifying states. This threshold was lower than unanimous approval, allowing the new framework of government to proceed despite opposition in several states.
Delaware became the first state to ratify, on December 7, 1787. New Hampshire supplied the decisive ninth ratification on June 21, 1788, placing the Constitution into effect. Virginia and New York followed soon afterward, while North Carolina and Rhode Island waited longer.
The number nine is sometimes confused with eleven, the number of states whose ratifications Congress had certified by September 1788 when it organized the new federal government. Rhode Island, the thirteenth original state, did not ratify until May 29, 1790.