Mesa Verde, a large, gently sloping plateau etched with deep canyons, was occupied by the Ancestral Puebloan civilization between the sixth and thirteenth centuries A.D. Although the Ancestral Puebloans lived on the mesa tops and farmed the fertile soil for most of their history, during the late twelfth century they constructed settlements along the sides of the canyon walls, in alcoves high above the canyon floor. The largest and best known of them is Cliff Palace, a social and administrative center that contained 150 rooms and was occupied by 100 people. Few sandstone alcoves were large enough to accommodate structures of that size and most cliff dwellings were much smaller. The complexes had kivas, ceremonial underground structures with roofs forming open courtyards. However, within a century the population started migrating to the south, and the sites of Mesa Verde were abandoned. The settlement at Mesa Verde survived in a remarkable state of preservation for many centuries, but its condition has never been completely stable. Weather, age, and a lack of ongoing stabilization and routine maintenance were the primary threats.
Conserving one of the first World Heritage sites in the U.S.
First explored in the 19th century, Mesa Verde National Park was established in 1906. Today the park contains over 4,000 archaeological sites. It was included in the 1998 World Monuments Watch in order to call attention to collapsing walls, sagging roofs, and eroded mortars. In addition to structural issues, original earthen architectural finishes had deteriorated at an alarming rate. Between 1994 and 1996 researchers from the Architectural Conservation Laboratory of the University of Pennsylvania developed a model program for the documentation, conservation, and monitoring of plasters and other painted finishes in the park. In 1998, we helped implement this program which also provided training to students of architectural conservation in the treatment of earthen finishes. In 2001, with additional funding from American Express, we were involved with the documentation and conditions assessment at Spring House, a backcountry site not open to the public.
In 1978 Mesa Verde, along with Yellowstone National Park, became the first two sites in the United States to be inscribed in the UNESCO World Heritage List.