Formerly labeled Anasazi, the Ancestral Puebloan culture is the most widely known of the ancient cultures of Colorado. The people who built the cliff dwellings of Mesa Verde and the great houses of Chaco Canyon were subsistence farmers of corn, beans, and squash. The structures of this culture date to between ca. 350 BC and AD 1300 and are found throughout southwestern Colorado and other adjacent states of the Four Corners region. The great southward migration from this region by AD 1300 marks the end of the Ancestral Puebloan occupation in southwestern Colorado. The sites and histories of this ancestral culture are still valued today in song and prayer by the Pueblo peoples now residing in New Mexico and Arizona.

Ancestral Pueblo refers to both the ancient cultural tradition and the peoples once found in the Four Corners area of the American Southwest. It is one of three major cultural traditions defined by archaeologists in the four southwestern states (Arizona, Colorado, New Mexico, and Utah). The other two traditions are the Hohokam and Mogollon, neither of which extends into Colorado.

Early Archaeology and Terminology

Early investigators such as Richard Wetherill and Alfred V. Kidder referred to what we now call the Ancestral Pueblo tradition as the Anasazi. Although many early researchers drew inspiration from the historic Pueblos in their interpretations of the architecture and practices of the Ancestral Pueblo, they did not always make a clear link between this ancient culture and historic Pueblo peoples. They drew upon the Navajo workmen who helped them with some of their investigations and who called these ancient people ʾanaasází, translated as “old people,” “enemy ancestors,” or “ancient non-Navajos.” As archaeologists have increasingly associated many aspects of this ancient cultural tradition with the modern Pueblos, the term Ancestral Pueblo has gradually replaced Anasazi in archaeological literature as a more appropriate term.

The two branches of the Ancestral Pueblo tradition discussed in this summary—Mesa Verde and Chaco—are distinguishable from one another by differences in their pottery styles, architecture, and settlements, but they also shared a great deal in common.

The cultural diversity we see in the past is similar to modern Pueblo culture, which encompasses seven distinct languages and twenty-one pueblos, each under separate governance. They share a richly interwoven past. When Spanish conquistadors encountered the Pueblo groups in the sixteenth century, they found at least 50,000 to 60,000 people in approximately seventy-five Pueblo villages in what is now New Mexico and Arizona. Over the last 125 years, historians, archaeologists, and Pueblo tribal authorities have worked to untangle Ancestral Puebloan history to better understand how this tradition has shaped the customs and ways of life of modern Pueblo people.

All Pueblo culture shares in common an agricultural heritage focused on the cultivation of maize (corn) and a sedentary or semi-sedentary lifestyle centered on large village communities, or pueblos. The roots of this culture date back more than two millennia, to the very beginnings of agriculture and settled life in the northern Southwest.

Agriculture in the Northern Southwest (350 BC–AD 575)

The environment of the Four Corners made hunting and gathering difficult. The semiarid and arid upland landscape of the Colorado Plateau and Southern Rocky Mountains had patches of wild resources that were not reliable subsistence sources. In good years, the piñon nut harvest could be remarkable and large game such as mule deer, pronghorn, elk, and bighorn sheep offered fine hunting opportunities at certain times and locales throughout the year. But these resources, even when teamed with the wild grasses, berries, and other native plants of the area, necessitated a mobile lifestyle and tremendous seasonal flexibility. Consequently, the population was restricted to small groups that used particular areas seasonally. Climatic shifts also limited human occupation in the area.

Between about 2100 to 1200 BC, increasingly reliable summer precipitation and the introduction of maize from the south allowed for early horticulture. The first corn was not well adapted to the short growing seasons and dry climate, and the resulting corncobs were only an inch or two long. It would take 1,000–1,500 years before maize varieties were developed or introduced that could be successfully grown across a wide area.

Although the transition from a limited horticulture and seminomadic lifeway to a more dedicated and sedentary agricultural lifeway was slow, small farming communities emerged in the late Archaic to early Formative periods and the population began to increase steadily. In general, this early farming culture is still referred to as Basketmaker because basketry and woven goods remained the mainstays of storage, cooking, and serving vessels.

Between about 350–200 BC and AD 300–350, there was a notable increase in multi-season and multi-household residential sites in certain regions. Evidence at these sites shows that the inhabitants were more dependent on maize cultivation, supplemented by localized hunting and gathering. These early farmers invested energy in more substantial and weatherproof pithouses and large, secure cists for food storage. The trash heaps, or middens, at these early residential sites indicate the inhabitants were at least semisedentary, residing at a single location for more than half a year.

The southern half of the Ancestral Pueblo area in New Mexico and Arizona is a source of innovation and many changes in the period between AD 200 and 600. The earliest Basketmaker brown ware pottery originates here and serves as a model for the first pottery in the Mesa Verde region. The original development and most widespread use of large community structures called great kivas also occurred in the south. Finally, beans, which offered a critical dietary pairing with maize, were more widely distributed in the south in early Basketmaker times. The south offered a historically secure and possibly more resilient locale for early agriculture, and at least half of the early farming populations in the Mesa Verde region likely could trace their origins to south of the San Juan River.

Early Pueblos and Great Houses (AD 575–900)

The adoption of maize agriculture and the increasing use of beans and squash to achieve a more balanced diet helped to trigger a population increase, a demographic transition that characterizes many early agricultural societies. With decreased mobility, mothers can have and sustain more children and larger households are economically useful and viable.

By AD 600 the population south of the San Juan River had increased significantly, and immigrant populations began to move into the Mesa Verde region once again. The central part of this region holds evidence of early habitations built during the span of AD 575–700. Tree-ring and pollen records suggest that for much of the seventh century climatic conditions for farming would have been good in this region, and the immigrants were moving into a landscape rich in natural and wild resources. By AD 725–750, there were at least 4,500 people spread across the whole Mesa Verde region, from Elk Ridge north of Blanding, Utah, to the Animas River valley near Durango.

The settlements of the mid-seventh century were most commonly single-household or paired-household hamlets. Small villages of eight to ten pithouses are known, but these were exceptional. Equally rare were great kivas, immense pit structures that could be from ten to twenty meters in diameter. Rock art that dates to this period appears to portray community gatherings at great kivas and suggests the grand scale of these ritual events.

By AD 750, the first small room blocks that would have housed two to four individual families are evident, foreshadowing a significant transformation in how settlements will be organized. Within a single generation after this architectural change, the first large villages with ten to twenty or more households emerge. Some of the earliest villages in the Ancestral Pueblo area occur in eastern and western Mesa Verde by about AD 775.

The period between AD 775 and 875 saw significant demographic shifts across the whole Ancestral Pueblo area, continued population growth, and a concentration of population in the central Mesa Verde region when compared to other Pueblo regions. Migration from the peripheries to the center of the Mesa Verde region, along with natural reproduction, concentrated as many 12,000 people into clusters of compact villages by AD 875. A mix of styles in the architecture, pottery, basketry, and organization of these villages suggests diversity within the regional population.

The largest villages and the concentration of population in the Mesa Verde region lasted only two to three generations. After a demographic peak at approximately AD 860, the population began to decrease by 880, and by the middle of the next century, there were no more than 2,500 people in the core area of the Mesa Verde region. Social and environmental turmoil appear to have been accelerated by several extended periods of drought and shortened growing seasons, and three centuries of expanding human populations had taken a toll on the region’s natural resources, wild game, and clean water.

In addition, we see evidence of the failure of key sociopolitical organizations suggested by the ritual burning of specific community structures and patterned acts of ritual violence against particular individuals in villages with early great houses. Particular structures, which previously had been the center of community feasts and ritual events, were deliberately burned down when they were depopulated. The focus on specific structures and particular individuals suggests these were deliberate, internal acts. Apparently, the social “glue” and alliances within these community centers came apart under the stresses of the late ninth century.

Once again, the various Pueblo groups—with their particular histories, evolving languages, and increasingly interwoven traditions—chose to leave their communities in this region and head either west and southwest or south and southeast. It appears that out of the dust and ideas of these ninth-century Mesa Verde villages emerged the even greater houses of Chaco Canyon of the tenth and eleventh centuries.

The Chaco World (AD 900–1125)

In the tenth century the center of the Ancestral Pueblo world moved south of the San Juan River once again. The developments following the depopulation of the early Pueblo villages that resulted in the emergence of a southern great house system are still poorly understood. Current explanations argue that the large influx of people from the northern villages, combined with the germ of what was learned from the failure of the first great house experiments, gave rise to an organizational model in which great houses were placed at the center of a more dispersed rural community instead of within villages. Great houses were situated on prominent places within a landscape, and smaller residences were built around it. Between AD 900 and 1000, a great house system of over twenty-five communities appeared south of the San Juan, and throughout the period of AD 1020–1125. Chaco Canyon was the undisputed center of this system.

The Chaco system influenced and at least partially united—if not dominated—much of the northern Southwest for at least a century. This is one of many elements of Ancestral Puebloan history that helps us understand the extraordinarily entangled histories of the modern Pueblos.

During the century of the Chaco system’s florescence, the great houses in Chaco Canyon became truly monumental, rising four or five stories and having precisely laid masonry, massive walls, and striking symmetries. The reach of this system stretched from the Far View Group of sites at Mesa Verde National Park and Chimney Rock National Monument in the far north to the Andrews and Casamero sites near Grants, New Mexico, in the south. By AD 1125–1150, there may have been as many as 200 great houses aligned with or emulating this system.

Chaco’s century of prominence coincided with a regional population increase. Population rebounded in Mesa Verde and other regions that had seen significant population loss in the tenth century. We are still uncertain about the extent to which these outlying regions were connected to Chaco Canyon, but it is clear that many outlying great houses were built in the same fashion as the great houses of the canyon. By the mid-to-late 1000s, there was a clear and strong connection between Chaco Canyon and particular groups of sites, such as the Aztec complex of sites in New Mexico, just south of Durango along the Animas River.

Chaco’s Decline and the Last Migration from the North (AD 1125–1300)

The Southwest suffered one of the most severe droughts of the last millennium between AD 1130 and 1180. It is a period associated with a significant increase in violence, decreased population, and regional reorganization. Construction in Chaco Canyon all but ceased, and both its influence and population moved to other regions. It is uncertain whether the drought was the primary cause of Chaco’s dramatic decline or was simply one more factor bringing down a system that had become too top-heavy and costly for its adherents. Whatever the causes, Chaco’s decline was quick and decisive.

In the north, centers of influence emerged around Aztec—at the periphery of both the Chaco and Mesa Verde regional systems—and around several large Mesa Verde community centers, such as Yellow Jacket Pueblo and the Goodman Point–Shields Pueblo. The turbulence and violence of the late twelfth century subsided in the Mesa Verde region as Aztec’s leadership faltered and power struggles became more localized and smaller in scale. However, there still appears to have been a widespread perception of risk that may have propelled a growing number of people to seek refuge in large villages. The settlement pattern shifted from small villages on mesa tops close to farm fields to canyon rims closer to water and defensive positions. This shift resulted in significant increases in both the population and size of the largest villages, as outlying populations converged in the central Mesa Verde region.

Community architecture and religious practices also changed. Great houses were no longer constructed but in some areas were replaced by villages with multi-walled structures. Multi-walled structures are uncommon in the western Mesa Verde region and not found in the late Pueblo villages of Hovenweep National Monument. This absence is especially evident at western sites such as Lowry Pueblo that had large great houses only a century earlier.

After AD 1225 some villages, such as Yellow Jacket, became larger than the others. Village clusters became more tightly packed and competition for suitable agricultural land, trade partnerships, and access to wild resources and water appears to have intensified. The more competitive social landscape after AD 1250 is marked by a dramatic rise in the number of towers and walls dating to this period.

Population in the core of the Mesa Verde region appears to have peaked between AD 1225 and 1260 at an estimated 26,000, with certainly more than 30,000 people across the whole region. Soon thereafter, people began to leave. Emigration accelerated markedly once it began, and the collapse of settlements on the peripheries, such as those at Hovenweep, must have contributed to the chaos. People within or adjacent to what is now Mesa Verde National Park used the protection afforded by cliff dwellings and the advantage of nearby agricultural lands to hold on longer than many other settlements.

Some of the first sites investigated by the Wetherills and Gustaf Nordenskiöld, such as Spruce Tree House and Cliff Palace, may have been among the last communities to depopulate. The entire region was largely depopulated by AD 1290, only thirty or forty years after it had reached its highest population. Many of the most defining characteristics of Mesa Verde architecture, pottery, social organization, and material culture were left behind. Where did these Ancestral Puebloans go? Subtle clues within the material culture of later sites, along with histories of the Pueblos, have helped experts identify the places where these migrants settled. People from the western communities largely moved into what is now Arizona and forged new relationships and identities with the Hopi. Central and eastern Mesa Verde groups appear to have had connections with groups in northern New Mexico such as the Keresan Pueblos (e.g., Acoma, Santa Ana/Tamaya, or Zia) and Tewa Pueblos (e.g., Ohkay Owingeh, San Ildefonso, and Santa Clara).

Interestingly, one of the very last occupied sites, Yucca House, is likely mentioned in T19 Pueblos of New Mexico ewa oral history as being a place of the ancestors. It is also the only late Mesa Verde village where a portion of its layout is built in a style not commonly seen until fourteenth-century pueblos of northern New Mexico.

Although no single reason explains the final Mesa Verde migration, it is clear that social and political strife, the threat of violence, religious upheaval, and disruptions of interaction and trade networks all predate the most severe droughts of this period. The droughts must have been the final blow, especially with the promise of slightly better conditions to the south. Whether non-Pueblo groups—such as the Ute or Athapaskans—forced the Ancestral Pueblo people to leave the Mesa Verde region is an old hypothesis that still has some adherents, but today there is little archaeological evidence that these groups constituted a significant presence in the Mesa Verde region in AD 1280, when the last Puebloans were leaving.

With the depopulation of the Chaco, Mesa Verde, and other even more northerly regions and the establishment of the historically known pueblos of the Rio Grande and Little Colorado regions, the history of the Ancestral Pueblo becomes the “deep history” that is now remembered in the oral traditions of the modern Pueblo and researched by archaeologists and historians. These historic Pueblo groups built even larger villages and a more populous civilization, but structures of Mesa Verde and Chaco, as well as the lessons they offer, continue to intrigue us.