Delegates signed the United States Constitution on September 17, 1787.
The signing took place at Independence Hall in Philadelphia during the final session of the Constitutional Convention. Thirty-nine delegates endorsed the document, representing twelve states; Rhode Island had declined to send delegates. George Washington, the convention's presiding officer, signed first.
The convention originally met to revise the Articles of Confederation, but the delegates ultimately drafted an entirely new framework of government. The Constitution created a federal system with legislative, executive, and judicial branches. It was then sent to the states for ratification under a rule requiring approval from nine of the thirteen states.
Signing did not immediately make the Constitution effective. New Hampshire became the ninth state to ratify it on June 21, 1788, and the new federal government began operating on March 4, 1789. Three delegates who remained at the convention declined to sign: Edmund Randolph, George Mason, and Elbridge Gerry.