Between A.D. 1000 and 1050 the culture of the Anasazi reached its height and became stable for a few centuries, until about A.D. 1275-1300. Their homes were now substantial buildings of stone masonry, containing numerous adjoining rooms. Their kivas followed standard lines and were often incorporated in the house structures, though they were sometimes built as separate, semisubterranean chambers. No other abrupt changes or new forms distinguish this late period, which was essentially a continuation and fulfillment of earlier times. The large pueblos, most of which were begun about A.D. 1000, are the most outstanding development of this period. In Canyon de Chelly, construction was started on White House and Antelope House during these years. Other important population centers were developing simultaneously at Mesa Verde (Mesa Verde National Park, Colo.), where the largest concentration of surviving cliff dwellings is located, and at Chaco Canyon (Chaco Canyon National Monument, N. Mex.), where spacious apartment houses, one with more than 800 rooms, were constructed on the floor of the canyon. Other villages were built in the Kayenta-Marsh Pass area (near Navajo National Monument, Ariz.). As permanent homes gave them social stability and well-developed agriculture ensured adequate food, the Anasazi had leisure and sufficient security for greater activity in their arts, crafts, and ceremonials. As a consequence, trade with other peoples seems to have grown and flourished because it brought in the specialized and exotic materials needed for rituals and pleasure. Parrots were traded from Mexico for their plumage, and ornamental shells from the Gulf of California and the West Coast found their way to Anasazi settlements. Turquoise, jet, and salt also became important trade items. The mode of dress changed little. Feather-string blankets were still commonly worn in winter. Cotton became almost the only fiber used for making cloth. Sandals, which were woven from whole yucca leaves, were crude, compared to those of earlier periods. But painted pottery reached its highest development in both variety and quality. These great pueblo centers flourished for about two centuries. But this was a time of increasing dryness in the Southwest, and the end for these settlements came during a severe drought late in the 13th century. Tree-ring data indicate that there was not enough moisture to produce crops during most of the years between 1276 and 1299. The drought brought crop failures, and the ensuing erosion destroyed the fields. Hunger, decline, and migration followed. Family after family and group after group left their homes in the cliffs and canyons. Taking what few possessions they could carry on their backs, they drifted away in search of land with a dependable water supply suitable for farming.