Delegates signed the United States Constitution on September 17, 1787, a date connected to the founding history remembered during the Semiquincentennial.
The signing took place at the Pennsylvania State House in Philadelphia, after months of debate and negotiation at the Constitutional Convention. Thirty-nine delegates signed the document, while several others who had attended the convention declined to sign or were absent.
Signing did not immediately make the Constitution operative. It still required ratification by the states. The necessary ninth state, New Hampshire, ratified it on June 21, 1788, and the new federal government began operating in 1789.
September 17 is now observed in the United States as Constitution Day and Citizenship Day. It is often confused with July 4, 1776, the date associated with the Declaration of Independence rather than the Constitution.