Thirty-nine delegates signed the U.S. Constitution in Philadelphia on September 17, 1787.
The signing took place at the final session of the Constitutional Convention in what is now Independence Hall. The convention had involved 55 delegates at various points, but only 39 signed the completed document. George Washington, the convention’s president, signed first, followed by the other delegates.
Three delegates present at the final session—George Mason, Edmund Randolph, and Elbridge Gerry—refused to sign. Several delegates had already left Philadelphia, and Rhode Island had declined to send a delegation to the convention. The Constitution therefore was not signed by every participant or every state.
The document was then sent to the states for ratification. Article Seven required approval by conventions in nine states. New Hampshire supplied the ninth ratification in June 1788, while the final original state, Rhode Island, ratified in May 1790.