The United States Constitution was signed on September 17, 1787, a major milestone connected with America250 history.
The signing took place at the Pennsylvania State House, now called Independence Hall, in Philadelphia. Thirty-nine delegates endorsed the document after the Constitutional Convention had spent four months debating how to structure the new national government.
George Washington, who presided over the convention, signed first. The delegates then signed by state, moving generally from north to south. Rhode Island did not send delegates to the convention, so the signers represented twelve states.
The Constitution did not take effect immediately. New Hampshire became the ninth state to ratify it on June 21, 1788, providing the required threshold for implementation. The new federal government began operating in 1789, after the Constitution replaced the Articles of Confederation.