Section 14-1004-i of the Philadelphia code states: A building, complex of buildings, structure, site, object, or district may be designated for preservation if it:
(a) Has significant character, interest, or value as part of the development, heritage, or cultural characteristics of the City, Commonwealth, or nation or is associated with the life of a person significant in the past;
(b) Is associated with an event of importance to the history of the City, Commonwealth or Nation;
(c) Reflects the environment in an era characterized by a distinctive architectural style;
(d) Embodies distinguishing characteristics of an architectural style or engineering specimen;
(e) Is the work of a designer, architect, landscape architect or designer, or professional engineer whose work has significantly influenced the historical, architectural, economic, social, or cultural development of the City, Commonwealth, or nation;
(f) Contains elements of design, detail, materials, or craftsmanship that represent a significant innovation;
(g) Is part of or related to a square, park, or other distinctive area that should be preserved according to a historic, cultural, or architectural motif;
(h) Owing to its unique location or singular physical characteristic, represents an established and familiar visual feature of the neighborhood, community, or City;
(i) Has yielded, or may be likely to yield, information important in pre-history or history; or
(j) Exemplifies the cultural, political, economic, social, or historical heritage of the community.
For a few examples of properties that meet each of these criteria, see pages 6-7 of the Preservation Alliance’s How to Nominate an Individual Building, Structure, Site or Object to the Philadelphia Register of Historic Places.