The Birthplace of the Constitution

Philadelphia served as the de facto capital of the United States for much of the nation's early history, and both the Declaration of Independence and the U.S. Constitution were written and signed there. The Constitutional Convention, held at the Pennsylvania State House in the summer of 1787, produced the document that still governs the country. The debates were conducted in secret, with windows nailed shut during a Philadelphia summer to prevent eavesdroppers, a condition that Benjamin Franklin described as a veritable furnace. The result was a framework of government that has lasted longer than any other written national constitution in history.

Source: Wikipedia