How many states had to ratify the Constitution before it could take effect?

Nine states had to ratify the Constitution before it could take effect.

Article VII established the ratification threshold at nine of the 13 states. This was a major departure from the Articles of Confederation, which generally required the agreement of all states for important changes.

New Hampshire became the ninth state to ratify on June 21, 1788. Its action placed the Constitution into effect even though Virginia, New York, North Carolina, and Rhode Island had not yet ratified. The remaining states eventually joined the constitutional system.

The number is often confused with either 13, the number of original states, or a simple majority of seven. Neither is correct for Article VII. The nine-state rule allowed the new government to proceed while leaving room for the remaining states to decide whether to join.