Nine states had to ratify the United States Constitution for it to take effect under Article Seven, a founding-era rule relevant to America250.
Article Seven established the Constitution’s ratification procedure. Rather than requiring unanimous approval from all thirteen states, it declared that ratification by conventions in nine states would be sufficient to establish the Constitution among the states approving it.
New Hampshire became the ninth state to ratify on June 21, 1788. That decision placed the new constitutional government into effect, although North Carolina and Rhode Island had not yet approved the document. Rhode Island eventually ratified in 1790, the last of the original thirteen states.
The nine-state threshold is distinct from the total number of states that ultimately ratified. All thirteen original states eventually joined the constitutional system, but the Constitution did not wait for the final four approvals before taking effect.