Thirty-nine delegates signed the U.S. Constitution on September 17, 1787. The signing took place at Independence Hall in Philadelphia at the final session of the Constitutional Convention.
Fifty-five delegates participated in the convention at some point, but not all remained through the final signing. Three delegates who were still present refused to sign: George Mason, Edmund Randolph, and Elbridge Gerry. Several others had already departed, which explains why the number of signers is lower than the number of convention participants.
The convention represented twelve states because Rhode Island declined to send delegates. The Constitution’s final signing group therefore did not include representatives from every original state, even though all thirteen later took part in ratification.
George Washington, the convention’s presiding officer, signed first. The document then went to the Confederation Congress and onward to state conventions. Ratification, rather than the signing ceremony alone, determined whether the Constitution would take effect.