For America250, on what date did the United States Constitution receive its final signature?

For America250, the United States Constitution received its final convention signatures on September 17, 1787.

The signing occurred during the final session of the Constitutional Convention at Independence Hall in Philadelphia. Thirty-nine delegates endorsed the document, which established a federal government with legislative, executive, and judicial branches. The convention then adjourned after completing its work.

Signing did not immediately make the Constitution the nation’s operating law. Article Seven required ratification by conventions in at least nine states. New Hampshire supplied the decisive ninth ratification on June 21, 1788, and the new government began under the Constitution in 1789.

The date can be confused with September 17, 1787, as a general “ratification” date, but ratification happened state by state over the following months. It can also be confused with June 21, 1788, when the required ninth state ratified. Constitution Day commemorates the 1787 signing and the document’s enduring role in American government.