Thirty-nine delegates signed the United States Constitution on September 17, 1787.
The signatures came at the end of the Constitutional Convention in Philadelphia. The convention had included more delegates over its four-month session, but not everyone who attended ultimately endorsed the final document. Three delegates present at the closing refused to sign: George Mason, Edmund Randolph, and Elbridge Gerry.
The 39 signers represented 12 states. Rhode Island did not participate in the convention, and New York’s Alexander Hamilton signed even though two other New York delegates, Robert Yates and John Lansing Jr., had left before the final signing. The parchment was then sent to Congress for distribution to the states.
The number 39 is sometimes confused with the total number of delegates who attended, or with the 55 delegates often cited as having attended at some point. It is specifically the number whose names appear as signers of the Constitution.