The United States Constitution was signed at Independence Hall on September 17, 1787, a key founding milestone before America250.
The signing concluded the Constitutional Convention in Philadelphia. Delegates had met for about four months to replace the Articles of Confederation with a stronger federal framework. George Washington presided over the convention and signed the final document.
Fifty-five delegates attended the convention at some point, but only 39 signed the Constitution. Rhode Island did not send delegates, so twelve states were represented at the signing. Three delegates who remained until the end declined to sign.
The Constitution did not take effect immediately. It required ratification by nine states and began operating in 1789. This date is often confused with July 4, 1776, which marks the Declaration of Independence, or April 30, 1789, when Washington was inaugurated.