Article Seven required nine states to ratify the United States Constitution before it could take effect among the ratifying states. The provision was designed to avoid requiring unanimous approval from all thirteen states.
The framers chose a state-convention process rather than relying solely on existing state legislatures. Article Seven stated that ratification by conventions in nine states would be sufficient to establish the Constitution between those states.
New Hampshire became the ninth state to ratify on June 21, 1788. That decision placed the Constitution into operation, although several states had not yet approved it. Virginia and New York ratified soon afterward, while North Carolina and Rhode Island waited until later.
Nine was a compromise between requiring too little support and demanding unanimity, which had been required under the Articles of Confederation for certain major decisions. All thirteen original states eventually ratified, but the constitutional government began before that process was complete.