On what date was the U.S. Constitution signed at Independence Hall?

The U.S. Constitution was signed at Independence Hall on September 17, 1787. The signing concluded the Constitutional Convention in Philadelphia.

Delegates had gathered to address weaknesses in the Articles of Confederation, but they ultimately produced an entirely new framework for the federal government. The convention met from May 25 through September 17, with George Washington presiding.

The signing date is different from the date the Constitution became operative. Article Seven required ratification by nine states, and that threshold was reached when New Hampshire ratified on June 21, 1788. The new federal government began operating in 1789.

September 17 is now observed in the United States as Constitution Day and Citizenship Day. July 4, 1776, instead marks adoption of the Declaration of Independence, not the Constitution’s signing.