Thirty-nine delegates signed the United States Constitution at the end of the 1787 Constitutional Convention.
The signing took place on September 17, 1787, at Independence Hall in Philadelphia. The convention had met for four months to address weaknesses in the Articles of Confederation, but it ultimately produced an entirely new framework for the federal government.
The 39 signers represented 12 states. Rhode Island declined to send delegates to the convention. Some delegates had already departed before the final session, and three delegates who remained refused to sign: George Mason, Edmund Randolph, and Elbridge Gerry.
The Constitution was then sent to the states for ratification. Article VII required approval by nine of the 13 states, rather than unanimous consent. New Hampshire became the ninth state to ratify on June 21, 1788, allowing the Constitution to take effect after the remaining ratifications followed. The number 39 refers specifically to delegates who signed, not the total number who attended the convention.