The Signing of the United States Constitution occurred on September 17, 1787, at Independence Hall in Philadelphia, Pennsylvania, when 39 delegates to the Constitutional Convention, representing 12 states (all but Rhode Island, which declined to send delegates), endorsed the Constitution created during the four-month-long convention. 

The language of the concluding endorsement, conceived by Gouverneur Morris and presented to the convention by Benjamin Franklin, was made intentionally ambiguous in hopes of winning over the votes of dissenting delegates. Jonathan Dayton, age 26, was the youngest to sign the Constitution, while Benjamin Franklin, age 81, was the oldest.