New Hampshire became the ninth state to ratify the United States Constitution, putting it into effect on June 21, 1788.
Article Seven specified that ratification by nine states would be sufficient for the Constitution to take effect among the states approving it. New Hampshire's convention therefore supplied the decisive ninth ratification, even though four states had not yet approved the document.
The Constitution had been signed in Philadelphia on September 17, 1787, and then sent to state conventions for consideration. Ratification was politically contentious, producing debates between Federalists, who supported the proposed government, and Anti-Federalists, who feared excessive central power.
Virginia ratified shortly after New Hampshire, followed by New York. North Carolina and Rhode Island were the last of the original thirteen states to ratify. The nine-state rule was an important departure from the Articles of Confederation, which required unanimous approval for major changes.