The historical document signed in 1787 was the United States Constitution. This foundational document established the framework for the federal government of the United States and outlined the rights of the states and the rights of citizens. The Constitutional Convention, held in Philadelphia, aimed to create a stronger federal structure to address the weaknesses of the Articles of Confederation. The Constitution has since become a pivotal reference for democratic governance, establishing principles such as separation of powers, checks and balances, and the protection of individual liberties, significantly impacting the development of modern democratic systems worldwide.