Thirty-nine delegates signed the United States Constitution at Independence Hall on September 17, 1787.
The signing occurred during the final session of the Constitutional Convention in Philadelphia. The delegates represented twelve states; Rhode Island had declined to send delegates to the convention. Although 55 delegates attended at some point during the convention, only 39 ultimately signed the completed document.
The number is sometimes confused with 42, the number of delegates still present when the signing took place, or with 55, the number who attended the convention. Three delegates who were present—George Mason, Edmund Randolph, and Elbridge Gerry—refused to sign. John Dickinson was absent because of illness, and George Read signed for him by proxy.
George Washington, who presided over the convention, signed first. Benjamin Franklin, aged 81, was the oldest signer, while Jonathan Dayton, aged 26, was the youngest. The document was then sent to the states for ratification rather than becoming effective solely through the Philadelphia signing.