Thirty-nine delegates signed the U.S. Constitution on September 17, 1787.
The signing took place at Independence Hall in Philadelphia at the close of the Constitutional Convention. Although 74 delegates had been selected, 55 attended at some point, and only 39 ultimately signed the document.
Three delegates who remained at the convention declined to sign: George Mason, Edmund Randolph, and Elbridge Gerry. Others had departed before the final ceremony, while Rhode Island had not sent delegates to the convention at all.
George Washington, the convention's presiding officer, signed first. Benjamin Franklin, aged 81, was the oldest signer, and Jonathan Dayton, aged 26, was the youngest. The Constitution still required ratification by state conventions before it could become the framework of the new federal government.