Philadelphia hosted the 1787 Constitutional Convention.
Delegates met at the Pennsylvania State House, now known as Independence Hall, from May 25 through September 17, 1787. The convention was initially called to revise the Articles of Confederation, but the delegates instead drafted an entirely new framework for national government.
George Washington presided over the meetings. James Madison played a major role in developing the Virginia Plan and is often called the “Father of the Constitution,” while Gouverneur Morris helped shape the final wording of the document. Fifty-five delegates attended at least some sessions, although only 39 ultimately signed the Constitution.
The convention’s work created the federal structure of the United States, including separate legislative, executive, and judicial branches. The Constitution was not effective immediately: it required ratification by the states. Philadelphia’s role can be confused with New York City’s role as the first capital under the Constitution, but the constitutional drafting convention itself took place in Philadelphia.