The United States Constitution was signed on September 17, 1787, a founding milestone connected with America's 250th anniversary.
Delegates signed the Constitution at Independence Hall in Philadelphia at the final session of the Constitutional Convention. The convention had met for four months to replace the Articles of Confederation with a stronger federal framework.
Thirty-nine delegates endorsed the final document. The convention represented twelve states because Rhode Island declined to send delegates. George Washington, who presided over the convention, signed first among the delegates listed on the document.
The Constitution did not take effect immediately upon signing. It required ratification by the states, and New Hampshire became the ninth state to ratify on June 21, 1788, providing the threshold required by Article VII. The new federal government began operating in 1789.