The major historical document signed in 1787 in Philadelphia was the United States Constitution. This document established the framework for the federal government and the system of checks and balances that define American democracy today. Created during the Constitutional Convention, the Constitution set forth the structure of the legislative, executive, and judicial branches while outlining the powers and responsibilities of each. It also included the Bill of Rights, ratified later in 1791, which guaranteed fundamental rights to individuals. The Constitution has since served as a model for democratic governance worldwide and remains pivotal in U.S. law and political evolution.