Thirty-nine delegates signed America's Constitution in 1787.
The signing took place on September 17, 1787, at Independence Hall in Philadelphia, where the Constitutional Convention had met. The delegates endorsed the completed document after months of debate over the structure and powers of the new federal government.
The 39 signers represented 12 states. Rhode Island did not send delegates to the convention, and several delegates who attended refused to sign the final Constitution. The document therefore reflected agreement among many participants, but not unanimity among everyone involved.
The Constitution still required ratification by the states before it could take effect. New Hampshire became the decisive ninth state to ratify it on June 21, 1788. The new federal government began operating under the Constitution in 1789.