The United States Constitution was signed on September 17, 1787, a milestone in the nation’s history marked by America250.
Delegates signed the Constitution at the Pennsylvania State House in Philadelphia, the same building now called Independence Hall. The Constitutional Convention had met there from May through September 1787 to replace the Articles of Confederation with a stronger federal framework.
George Washington, president of the convention, signed first. Thirty-nine delegates signed the document, while three delegates present at the final session—George Mason, Edmund Randolph, and Elbridge Gerry—refused to sign because they opposed parts of it.
The Constitution did not take effect immediately on the signing date. It required ratification by the states, and the new federal government began operating in 1789. September 17 is observed annually in the United States as Constitution Day and Citizenship Day.