Constitution Day and Citizenship Day is observed each year on September 17 to commemorate the signing of the Constitution on September 17, 1787, and “recognize all who, by coming of age or by naturalization, have become citizens.”
"September 17th is Constitution Day. America celebrates this day to commemorate when delegates came together in Philadelphia at the Constitutional Convention in 1787 and signed the U.S. Constitution into law. However, it wasn’t until 2004 that the holiday took on the full name it bears today. In 2004, Senator Robert Byrd passed an amendment renaming the holiday “Constitution Day and Citizenship Day,” which requires public schools and institutions to provide information on the history of the country’s Constitution.