Article Seven of the United States Constitution made ratification by nine states sufficient for the Constitution to take effect. It also prescribed that state conventions, rather than ordinary state legislatures, would ratify the document.
The provision was controversial because the Articles of Confederation had required unanimous approval for major changes. Article Seven instead created a threshold of nine states, allowing the new government to begin even if all thirteen original states had not yet agreed. New Hampshire became the ninth state to ratify on June 21, 1788.
The Constitution therefore took effect before North Carolina and Rhode Island had ratified it. North Carolina joined in November 1789, while Rhode Island became the final original state to ratify on May 29, 1790. Article Seven is separate from Article Five, which explains how constitutional amendments are proposed and ratified. That distinction is a frequent source of confusion when studying the Constitution during America250 commemorations.