Chaco Canyon was a major center of ancestral Puebloan culture between AD 850 and 1250. It was a hub of ceremony, trade, and administration for the prehistoric Four Corners area. Chaco is remarkable for its monumental public and ceremonial buildings, and its distinctive architecture. To construct the buildings, along with the associated Chacoan roads, ramps, dams, and mounds, required a great deal of well organized and skillful planning, designing, resource gathering, and construction. The Chacoan people combined pre-planned architectural designs, astronomical alignments, geometry, landscaping, and engineering to create an ancient urban center of spectacular public architecture. The Chacoan cultural sites are fragile and irreplaceable and represent a significant part of America's cultural heritage. The sites are part of the sacred homeland of Pueblo Indian peoples of New Mexico, the Hopi Indians of Arizona, and the Navajo Indians of the Southwest, all of whom continue to respect and honor them. Chaco Canyon is located in northwestern New Mexico.