Constitution Day (or Citizenship Day) is an American federal observance that recognizes the ratification of the United States Constitution and those who have become U.S. citizens. It is usually observed on September 17, the day the U.S. Constitutional Convention signed the Constitution in 1787. The law establishing the holiday was created in 2004 with the passage of an amendment by Senator Robert Byrd to the Omnibus spending bill of 2004.

For more information about Constitution Day, visit the Constitution Center's Constitution Day page here. To learn more about the rich history of the U.S. Constitution visit www.constitutioncenter.org. The National Constitution Center is an independent, non-partisan, and non-profit organization dedicated to increasing public understanding of, and appreciation for, the Constitution, its history, and its contemporary relevance, through an interactive, interpretive facility within Independence National Historic Park and a program of national outreach.

The Centuries of Citizenship: A Constitutional Timeline is an online experience highlighting some of the key dates and events that mark more than 200 years of our constitutional history. These timeline entries, taken as a whole, tell the evolving story of the U.S. Constitution and the continuing role that it plays in our lives. Take part in the online experience.

Additional information can be found at the Library of Congress repository for Constitutional documents and information and the National Archives website for the U.S. Constitution.