When was the United States Constitution signed at the Philadelphia Convention?

The United States Constitution was signed at the Philadelphia Convention on September 17, 1787.

The signing took place at Independence Hall, where delegates had spent four months debating how to replace the Articles of Confederation. George Washington presided over the convention and signed first. The final document created a federal system with separate legislative, executive, and judicial branches, subject to later ratification by the states.

Thirty-nine delegates signed the Constitution, representing twelve states. Rhode Island did not send delegates to the convention. Not every delegate who attended approved the final document: three delegates present refused to sign, including George Mason, Edmund Randolph, and Elbridge Gerry. The Constitution became effective after New Hampshire supplied the ninth state ratification in June 1788, and the new federal government began operating in 1789.