On what date was the United States Constitution signed by delegates at the Philadelphia Convention?

The United States Constitution was signed by delegates at the Philadelphia Convention on September 17, 1787.

Delegates had met in Philadelphia beginning in May 1787 to revise the Articles of Confederation, but they produced an entirely new framework for the federal government. The final document was signed at the Pennsylvania State House, now known as Independence Hall.

Thirty-nine delegates signed the Constitution. George Washington presided over the convention, while Benjamin Franklin was among the older delegates present. The document then went to the states for ratification rather than taking effect immediately on the signing date.

September 17 is observed in the United States as Constitution Day and Citizenship Day. It is distinct from July 4, 1776, the date associated with the Declaration of Independence, and from June 21, 1788, when New Hampshire supplied the ninth ratification needed for the Constitution to take effect.