Thirty-nine delegates endorsed the United States Constitution at its signing on September 17, 1787.
The signing took place at Independence Hall in Philadelphia after the Constitutional Convention had met for four months. The delegates represented 12 states; Rhode Island declined to send delegates to the convention. George Washington, the convention’s presiding officer, signed first.
The Constitution’s closing statement recorded that the document was completed by the unanimous consent of the states present. Although 55 delegates attended at some point during the convention, only 39 signed the final document. Three delegates present—George Mason, Edmund Randolph, and Elbridge Gerry—refused to sign.
The signing did not immediately put the Constitution into operation. Ratification by the states was still required, and the new federal government began functioning in 1789. The event is distinct from the later Bill of Rights, which became the first ten amendments in 1791.