Delegates signed the United States Constitution on September 17, 1787.
The signing concluded the Constitutional Convention at Independence Hall in Philadelphia. Thirty-nine delegates signed the document, representing twelve states; Rhode Island had declined to send delegates to the convention.
The Constitution did not immediately begin operating as the federal government. Article VII required ratification by nine states, which New Hampshire supplied on June 21, 1788. The new government began operating under the Constitution on March 4, 1789.
The signing date is sometimes confused with the Declaration of Independence's July 4 date or with the Constitution's ratification dates. George Washington, president of the convention, signed the document, as did Benjamin Franklin, James Madison, Alexander Hamilton, and other delegates. The convention's final document contained seven articles.