Nine states had ratified the United States Constitution when it took effect in 1788. Article Seven required ratification by conventions in nine states before the Constitution could become effective among the ratifying states.
Delaware was the first to ratify, on December 7, 1787. New Hampshire became the ninth on June 21, 1788, providing the constitutional threshold. The new federal government began operating in 1789, after North Carolina and Rhode Island had also ratified.
The ratification process was fiercely debated. Federalists supported a stronger national government, while Anti-Federalists feared excessive central authority and the absence of a bill of rights. The promise that amendments would be added helped build support in several states.
Nine is sometimes confused with the thirteen states that eventually joined the constitutional system. The Constitution did not require unanimous approval, unlike the Articles of Confederation, which had required all states to agree to major changes. North Carolina ratified in 1789 and Rhode Island in 1790.