Integrity, as every student of the National Register learns, is the ability of a property to convey its historical significance. Integrity is characterized by the National Register as having seven aspects (materials, workmanship, setting, design, location, feeling, and association), and has, at times, been criticized because of its inherently subjective qualities. The seven aspects of integrity contain five “hardware” components-values that could be enumerated, such as materials and design-and two “software” components (feeling and association) that resist quantification. During the prehistory of the National Register, the Park Service was equally concerned with the issues of a property’s “authenticity of association” as well as its “integrity of fabric.”1 Defining parameters for integrity was closely related to how preservationists approached the reconstruction and adaptive use of historic properties. Because preservationists have avoided refining or quantifying objective measures for a property’s integrity, as a term of art, the concept is like the proverbial “Jello on the wall:” it is hard to nail down.