On what date was the United States Constitution signed at the 1787 Constitutional Convention?

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

The signing took place at the final session of the Constitutional Convention. Delegates had met for four months to address weaknesses in the Articles of Confederation, but they ultimately designed a new system with a stronger federal government.

Thirty-nine delegates signed the document, representing twelve states. Rhode Island had declined to send delegates, and three delegates who attended the final session refused to sign. George Washington, who presided over the convention, signed first.

The signed Constitution was then submitted to state conventions for ratification under its Article Seven. It became effective after the required states ratified it, and the new federal government began operating in 1789. The anniversary of the signing is now observed as Constitution Day in the United States.