The U.S. Constitution was signed by the delegates at Philadelphia in 1787.
The Constitutional Convention met from May 25 to September 17, 1787. Delegates from twelve states attended at different times; Rhode Island sent no delegates. The convention produced a new framework for the federal government, including separate legislative, executive, and judicial branches.
Thirty-nine delegates signed the finished document on September 17, 1787. George Washington, who chaired the convention, signed first. The document then went to the states for ratification rather than taking effect automatically.
The Constitution became operational in 1789 after the necessary ratifications and the organization of the new government. The year 1776 belongs to the Declaration of Independence, 1781 to the Articles of Confederation’s ratification, and 1789 to the beginning of the constitutional government.