On what date was the United States Constitution signed at Independence Hall?

The United States Constitution was signed at Independence Hall on September 17, 1787.

The signing concluded the Constitutional Convention in Philadelphia, which had met from May 25 through September 17. Thirty-nine delegates endorsed the document, representing twelve states; Rhode Island had declined to send delegates. George Washington, the convention’s president, signed first.

The signing date is often confused with ratification or the start of the new federal government. New Hampshire became the ninth state to ratify on June 21, 1788, satisfying Article VII’s requirement, but the Constitution’s government began operating on March 4, 1789. Constitution Day in the United States is observed annually on September 17.