On what date did delegates sign the United States Constitution?

Delegates signed the United States Constitution on September 17, 1787.

The signing took place at the Pennsylvania State House in Philadelphia, later known as Independence Hall. It concluded the Constitutional Convention, which had met during the summer to design a stronger national government than the Articles of Confederation provided.

Thirty-nine delegates endorsed the final document. George Washington, who chaired the convention, signed first. Benjamin Franklin, then 81, was the oldest signer, while Jonathan Dayton, 26, was the youngest. Rhode Island did not send delegates to the convention.

The signing date is distinct from ratification. The Constitution required approval by nine states and reached that threshold on June 21, 1788, when New Hampshire ratified it. The federal government began operating under the Constitution on March 4, 1789, making 1787 an important neighboring milestone to the 1776 anniversary.