September 17 is Constitution Day and Citizenship Day! This day commemorates the signing of the United States Constitution on September 17, 1787, and recognizes all who have become United States citizens.
In 1940, Congress requested that the President issue a proclamation designating the third Sunday in May as "I Am An American Day" to recognize all who had attained citizenship. In 1952, Congress repealed this and passed a new resolution moving the day to September 17 to coincide with the signing of the Constitution. In 2004, the day was officially recognized as "Constitution Day and Citizenship Day."
For more information on the history and to view the government documents related to Constitution Day and Citizenship Day, visit the Law Library of Congress.