On what date did 39 delegates sign the United States Constitution at Philadelphia’s Independence Hall?

Thirty-nine delegates signed the United States Constitution at Independence Hall on September 17, 1787.

The signing concluded the Constitutional Convention in Philadelphia after nearly four months of debate. The delegates endorsed a new federal framework with separate legislative, executive, and judicial branches and a system of shared power between the national government and the states.

The 39 signers represented twelve states; Rhode Island had declined to send delegates to the convention. Not every delegate who attended signed the document, including George Mason, Elbridge Gerry, and Edmund Randolph, who objected for different reasons.

The signing did not immediately put the Constitution into operation. Ratification by conventions in at least nine states was required, and the new government began operating in 1789 after the ratification process was completed.