The Pecos Classification System, used to more easily compare archaeological information with other areas of the Southwest, categorizes pre-Columbian sites into time periods based on absolute dates (from tree-rings, etc.) and on cross-dating using architectural remains, artifacts, and other cultural indicators. However, sites in Chaco are particularly complex, in part due to dense and lengthy occupation of the Canyon. In addition, a site as simple as a single component habitation or as complex as a 600 room multi-component structure can have meaning in any or all of the following categories: archaeological site, architectural monument, historic structure, ethnographic resource, sacred site/shrine and/or traditional cultural property, cultural landscape element, and more. Although some have relatively simple histories, their contexts in time and space have value and meaning to descendants, scholars, visitors, and a world-wide public.