The United States Constitution went into effect on March 4, 1789, when the new government began operating under the Constitution after the ninth state, New Hampshire, ratified it on June 21, 1788. The Constitution was signed on September 17, 1787, but it required ratification by nine states to become the official framework of the government. The ratification of New Hampshire as the ninth state met that requirement, and March 4, 1789, was set as the date for the new government to start functioning under the Constitution.
