The United States Constitution was signed at Independence Hall on September 17, 1787.
The signing concluded the Constitutional Convention in Philadelphia, which had met for four months to design a new federal government. Delegates had originally been authorized to revise the Articles of Confederation, but they ultimately produced an entirely new constitutional framework.
Thirty-nine delegates signed the Constitution on September 17. They represented twelve states; Rhode Island had declined to send delegates to the convention. George Washington, who chaired the convention, signed along with other prominent delegates including Benjamin Franklin and James Madison.
September 17 is now observed in the United States as Constitution Day and Citizenship Day. It is distinct from July 4, 1776, when the Declaration of Independence was adopted, and from March 4, 1789, when the Constitution’s new federal government began operating.