Chicago Landmark is a designation by the Mayor and the City Council of Chicago for historic sites in Chicago, Illinois, United States. Listed sites are selected after meeting a combination of criteria, including historical, economic, architectural, artistic, cultural, and social values. Once a site is designated as a landmark, it is subject to the Chicago Landmarks Ordinance, which requires that any alterations beyond routine maintenance, up to and including demolition, must have their permit reviewed by the Landmarks Commission. Many Chicago Landmarks are also listed on the National Register of Historic Places, providing federal tax support for preservation, and some are further designated National Historic Landmarks, providing additional federal oversight. Criteria The Mayor and the City Council appoint a nine-member Commission on Chicago Landmarks to develop landmark recommendations in accordance with a 1968 Chicago city ordinance. The commission considers areas, districts, places, buildings, structures, works of art, and other objects within the City of Chicago for nomination based solely on whether each meets two or more of the following criteria: Its value as an example of the architectural, cultural, economical, historical, social, or other aspect of the heritage of the City of Chicago, State of Illinois, or the United States; Its location as a site of a significant historic event which may or may not have taken place within or involved the use of any existing improvements; Its identification with a person or persons who significantly contributed to architectural, cultural, economic, historic, social, or other aspect of the development of the City of Chicago, State of Illinois, or the United States; Its exemplification of an architectural type or style distinguished by innovation, rarity, uniqueness, or overall quality of design, detail, materials or craftsmanship; Its identification as the work of an architect, designer, engineer, or builder whose individual work is significant in the history or development of the City of Chicago, the State of Illinois, or the United States; Its representation of an architectural, cultural, economic, historic, social, or other theme expressed through distinctive areas, districts, places, buildings, structures, works of art, or other objects that may or may not be contiguous; Its unique location or distinctive physical appearance or presence representing an established and familiar visual feature of a neighborhood, community, or the City of Chicago. Once the commission has determined that a candidate meets at least two of the above criteria, the group may provide a preliminary landmark designation