The gradual infilling of persistent medieval property parcels in many European cities has made it possible to reconstruct urban growth and economic change by meticulous attention to morphological detail. A property may have been the site of a number of buildings through several centuries, and the amount of building coverage on a plot may ebb and flow, as the repletion cycle for burgages suggests (M. R. G. Conzen 1962). Nevertheless, property parcels (and street outlines) seem eternal. For the most part, this is because constraints of building technology often kept structures within existing property envelopes; the property and land markets were stable; and the pace of economic change was relatively slow (Vance 1971). By contrast, in the downtowns of American cities, the pace of change was rapid; the scale of rebuilding was revolutionary as new technologies developed; and the property market was volatile in an era of adjustments to the demands and opportunities of an expanding national urban system (M. P. Conzen 1987; Vance 1990). Original property parcels were often quickly obliterated. Demolition rather than adaptive reuse has long been the norm in American cities and, as key sites were redeveloped at the end of the nineteenth century, horizontal property expansion went hand in hand with vertical growth. In relative terms, therefore, the cadastral frame in American cities does not survive long enough to be used as a container and recorder of long-term historical urban change. Yet this frame is still extremely useful to portray the extent of short-term transformations and, when used in conjunction with archival records of real-estate transactions and corporate business histories, it can assist in the understanding of complex change.