The National Archives Building, known informally as Archives I, located north of the National Mall on Constitution Avenue in Washington, D.C., opened as its original headquarters in 1935. It holds the original copies of the three main formative documents of the United States and its government: the Declaration of Independence, the Constitution, and the Bill of Rights. It also hosts a copy of the 1297 Magna Carta confirmed by Edward I. These are displayed to the public in the main chamber of the National Archives, which is called the Rotunda for the Charters of Freedom. The National Archives Building also exhibits other important American historical documents such as the Louisiana Purchase Treaty, the Emancipation Proclamation, and collections of photography and other historically and culturally significant American artifacts.