Thirty-nine delegates signed the United States Constitution on September 17, 1787.
The Constitutional Convention originally involved 55 delegates who attended at least part of its proceedings. By the final day, some had departed, and three delegates who remained—Edmund Randolph, George Mason, and Elbridge Gerry—refused to sign. The 39 signatures therefore represent the delegates who endorsed the final document, rather than everyone who participated.
The signers represented twelve states because Rhode Island did not send delegates. John Dickinson was absent because of illness, but George Read signed on his behalf. Convention secretary William Jackson also signed to authenticate corrections, although he was not counted among the 39 delegates.
The group included figures later remembered as major Founders. George Washington signed as convention president, while Benjamin Franklin was the oldest signer at 81. Jonathan Dayton, aged 26, was the youngest. The final document then went to the states for ratification, a separate process from signing.