Of 55 people who attended to constitution convention who was the last survivor?

Answer 1

Since he was the youngest of the 55 at age 26, and he lived to be 63, I'd guess it was Jonathan Dayton (October 16, 1760 – October 9, 1824) from the U.S. state of New Jersey.

Nope. I'm wrong

James Madison (March 16, 1751 – June 28, 1836) one of the Founding Fathers of the United States. Considered to be the "Father of the Constitution", he was the principal author of the document.

The Wiki source below confirms that Madison was the last to die. I should have checked this first. Instead, I looked up all 55 delegates. Good question worth a star.