September 17, 1787 is the birthday of our government, the date on which delegates to the Philadelphia Convention completed and signed the U.S. Constitution. The ideas on which America was founded -commitments to the rule of law, limited government and the ideals of liberty, equality and justice – are embodied in the Constitution, the oldest written constitution of any nation on earth. Constitution Day is intended to celebrate not only the birthday of our government, but the principles that make us Americans. Read more on our Founding Fathers and other historical notes.