Article VII, the shortest article, set the terms for the Constitution to take effect: ratification by nine of the thirteen states.
Ratification
The Ratification of the Conventions of nine States, shall be sufficient for the Establishment of this Constitution between the States so ratifying the Same.
Done in Convention by the Unanimous Consent of the States present the Seventeenth Day of September in the Year of our Lord one thousand seven hundred and Eighty seven and of the Independance of the United States of America the Twelfth.
The Signers
The Constitution was signed by 39 delegates, led by George Washington, President of the Convention and deputy from Virginia. Signatories included James Madison, Alexander Hamilton, Benjamin Franklin, and Gouverneur Morris, among delegates from twelve states (Rhode Island did not send delegates to the Convention).
New Hampshire became the decisive ninth state to ratify on June 21, 1788, bringing the Constitution into effect. The new government convened in 1789.
Source
Transcription adapted from the U.S. National Archives.