On what date did the United States Constitution get signed in Philadelphia?

The United States Constitution was signed in Philadelphia on September 17, 1787.

The signing took place at the Pennsylvania State House, now called Independence Hall, during the final session of the Constitutional Convention. Thirty-nine delegates endorsed the document, representing 12 states; Rhode Island had declined to send delegates.

The convention had originally been called to revise the Articles of Confederation, but the delegates instead created an entirely new framework for the federal government. George Washington, who chaired the convention, signed first. Three delegates present—Edmund Randolph, George Mason, and Elbridge Gerry—refused to sign.

Signing did not immediately make the Constitution operative. It still required ratification by the states. Article VII required approval from nine of the 13 states, and the Constitution took effect after New Hampshire became the ninth state to ratify it in June 1788.