taken from http://www.holidayinsights.com/
The Constitutional Congress held it's final meeting on September 17, 1787. Do you have any idea why? That's right! It was to sign the Constitution of the United States of America, a document for which they so painstakingly labored to create and perfect.
After the meeting there was still much to do. Individual states then had to meet and vote on it. The U.S. Constitution did not go into effect until two years later on March 4, 1789.