how many of the 55 delegates signed the constitution?

Out of the 55 delegates who attended the Constitutional Convention, 39 signed the U.S. Constitution.

Many of the 55 were present at various times, but not all stayed through to the end or agreed with the final document. When the signing took place on September 17, 1787, 41 delegates were present, and 38 of them personally signed while one additional signature (John Dickinson’s) was added by proxy, bringing the total number of signers to 39.