Four Corners National Parks
Chaco Culture National Historical Park

The Chaco Phenomenon

Like much of Anasazi world, the Chacoan Culture remains today filled with questions and shrouded in mystery. The series of great houses and roads that are the hallmarks of the "Chaco Phenomenon" represent a system of political and social complexity and structure not previously seen in North America.  

What prompted one group of Anasazis to settle in that desolate, wind-swept, high desert canyon in northern New Mexico? Why did they build the massive and monumental stone structures that we today know as "great houses?" How did they become the dominant center of a culture that today bears its name? Why did they build the famed Chacoan roads? What happened that they walked out the door one day, as it were, locked it behind them, and abandoned everything they had spent their lives and centuries building? 

There are theories and hypotheses that purport to answer these questions -- yet none really satisfies. While much is known, there is much more about the Chaco Phenomenon that remains uncertain and unknown.

Chaco Culture

On the windswept high desert plateau south of the San Juan River in northwestern New Mexico, Chaco Canyon was home to a culture that today bears its name. The Chacoans were part of the ancient Anasazi civilization (called Hisatsinom by the Hopi and Ancestral Puebloans by the current politically correct) who occupied the Four Corners region for over a thousand years until their abrupt "collapse" about 1125 A.D. 

From the mid-9th through mid-12th centuries, Chaco Canyon was the political and economic capital of the vanished Chacoan culture. What remains at Chaco Canyon today is the country's densest and most exceptional concentration of large, Anasazi pueblos or villages.

East Entrance to the Chaco Culture National Historical Park at Chaco Canyon, New Mexico  (Photo by Elizabeth VanderPutten, October 2000)

Chacoan Communities and Roads (NPS Map, 2000)
Click on image for enlargement

The Chacoan World

Chacoan culture's sphere of influence spanned 25,000 square miles, stretching down the San Juan Basin of New Mexico and across wide portions of Colorado, Utah, and Arizona.

Chaco rose to dominance in the 6th century and collapsed in the 12th century. During the intervening years, it influenced the art, architecture, and religious and public life of the estimated 5,000 persons who were living at any one time n 2,500 or more outlying settlements in the near-in Chacoan World. Chaco was, in the words of the NPS, "unlike anything before or since."

One distinguishing hallmark of Chacoan culture was the massive, pre-planned, multi-room stone building called the "great house." In Chaco Canyon they averaged more than 200 rooms each. Another distinguishing feature was its mysterious system of "roads."

The human and natural resources required for this construction was enormous. While many Chacoan scholars believe Anasazi culture was mainly non authoritarian, it is hard to imagine how the labor needed for these great houses, ramps, roads, dams, and related public building projects could have been accomplished otherwise.

Great Houses and Social Organization

Great houses were not homes, at least not full-time homes, and pueblos were not villages as we think of them. Rather, they were buildings and places where people gathered periodically for special ceremonial, trade and administrative events. In that sense, great houses were spectacular examples of public architecture, much as libraries, churches and state capitol buildings today are public architecture.

They reminded me in a way of downtown Atlanta after urban renewal in the 1960's. It was all office buildings and businesses. It was where people went to work but not to live. During the day the streets were busy. At night they were empty canyons.

Unlike most other early buildings, where a room was added as needed, great houses were unique for that time in that they were planned in advance and constructed over years and sometimes centuries. This required skilled planners, architects, and masons, and importantly it required an extraordinary level of social organization.

Pueblo Bonito

A Portion of the Great House, Pueblo Bonito
The boulders in the foreground are from a piece of the mesa that fell in 1941 and crushed the corner of Pueblo Bonito.. (Photo by Elizabeth VanderPutten, October 2000)
Click on image for enlargement

Sign at Pueblo Bonito
(Photo by Brian Larkin, October 2000)
Click on image for enlargement

Pueblo Bonito 

Pueblo Bonito was the biggest of the 12 great house in Chaco Canyon and the largest and tallest building in North America until the construction of the tall buildings in major cities at the end of the 19th century.

Around Pueblo Bonito and from Pueblo Bonito, Chacoan culture emanated. 

In addition to Pueblo Bonito in Chaco Canyon, there were "outlier" communities, each with its own huge great house. Beyond the canyon, more than 150 great house pueblos were built in near and far flung places across the Four Corners region. 

Pueblo Bonito

Pueblo Bonito is the best known of all Anasazi great houses, and has been studied by more researchers than almost any Western hemisphere site north of Mesoamerica. Begun in c. 850 A.D. it took three centuries to complete. When finished, it had perhaps 800 rooms as well as 2 central courtyards, 2 great kivas and 37 small kivas.

While Pueblo Bonito, like other great houses, was not built as a residence. its exact purpose or purposes is unknown and remains the subject of study and debate. When it was completed and before it was abandoned, it is believed that as many of 600 rooms may have been in use.

One line of thinking is that at least some, if not most, of the rooms in Pueblo Bonito and in all the great houses were used to store goods during times of plenty for use during times of shortages. This idea is consistent with food management and the variable climate and marginal rainfall.

In 1941, a huge sheet of rock pulled away from the mesa behind it and crushed the northeast corner of Pueblo Bonito.
Aerial view of Pueblo Bonito 1982 by the National Geographic Society
The Getty Conservation Institute Field Trip Report
Click on image for enlargement

(Photo by Elizabeth VanderPutten, October 2000)
Click on image for enlargement

Chacoan Architecture

Chacoan stone buildings were massive. They were larger than anything of their kind this country had ever seen. An 800-room, five-story, 70-foot-high stone complex was unparallel at the time. Egyptian pyramids were larger but of a different order; they were single purpose and simpler in concept though daunting in execution. Medieval European castles came closer.

Stone for Chaco great houses was quarried and shaped locally. The amount needed was staggering. The amount of wood used tells a story. 

Most of the wood used in the vigas (rafters or roofing beams) was ponderosa pine, some of which had to be hauled as much as 60 miles without draft animals or wheeled vehicles. During the 300 years of building the 12 great houses in Chaco Canyon, it is estimated that it took 200,000 trees. At an estimated 17-20 trees per acre, that is a lot of forest.

Chacoan Masonry Style

Chacoan style walls are called "core and veneer," which is easily distinguishable from other Anasazi styles such as Mesa Verde or Hovenweep. Basically, it is a three ply wall with the center or core made of rough rocks and the outer layers made of carefully shaped and fitted stones. 

In multi story buildings, some rising five stories, the walls on lower floors were triple thick to support higher floors. And walls tapered slightly inward as they rose. Both evidence detailed planning.

It is difficult to imagine how Chacoan architects were able to design these massive and complex buildings without geometry or other formal mathematics and without a written language. It is also difficult to imagine the level of skill their masons had. 

Over centuries, the Chacoan style evolved. The last is called McElmo and was used in the Kin Kletso great house. It was cruder and more like that of Mesa Verde with thick outer veneers of shaped sandstone and thin cores. One theory is that the best masons had left Chaco and were working at Aztec, which was undergoing a building boom.

Wall Detail at Pueblo Bonito
(Photo by Elizabeth VanderPutten, October 2000)
Click on image for enlargement

At the Edge of Pueblo Bonito
I am standing beside a partially restored wall at the edge of Pueblo Bonito. Behind me is the view that an ancient Chacoan would have seen of Fajado Butte guarding canyon's south entrance. (Photo by Brian Larkin, October 2000)
Click on image for enlargement

Roads of Chaco

From Chaco, an enigmatic series of roads stretch out into the desert. As the Park Service writes, "The true extent of the ancient Chacoan road system, as revealed by aerial photographs, impressed even veteran archeologists."   

Built in the 11th and 12th centuries, more than 400 miles of roads, some as much as 90 feet wide and averaging 30 feet in width, appear in segments in the immediate Chaco Canyon area and in scatted places in Southern Utah and Northern Arizona. 

An often noted feature of these roads is that they were carefully planned and engineered and most run in nearly arrow-straight lines. 

The longest road goes 42 miles north in the direction of Salmon Ruins and Aztec Ruins. On the north-south roads, settlements lay at travel intervals of approximately one day. 

Roads of Chaco

The Chacoan roads were not just hard worn foot paths, but meticulously surveyed and laboriously graded highways. They had no wheeled vehicles or draft animals. Everything was done by hand using only stone and wooden tools. Where roads ran over flat stone, low stone walls or lines of boulders were added. Where the topography sloped, the roadbed was leveled and a rock shoulder was built to hold the fill.

Traditional thought suggested these roads were built to facilitate trade with distant peoples (e.g., sea shells, turquoise found in burial sites) and communications and ties between outlying villages. During bountiful years, grain could have been stored in great houses and withdrawn during drought years. More recent research casts serious doubt about their use for trade and for grain redistribution..

Whatever their purposes, building them would be consistent with the political desire to bind Chacoans into a single society.

The Trail to Wijiji, a Great House and Observatory
I am standing at the Wijiji trailhead a short distance from Pueblo Bonito. Behind me is Fajada Butte with its Chacoan observatory and sun dagger.. Wijiji was a Chacoan "outlier" community (Photo by Brian Larkin, October 2000)
Click on image for enlargement

(Detail) Chacoan Roads Near Pueblo Alto
Click on image for enlargement

Chacoan Roads, Alternative Explanations

The conventional explanation for the roads of Chaco is simple and utilitarian, but in the end it is unsatisfying. It leaves too much unexplained. Early roads elsewhere typically follow natural paths. Most Chacoan roads were built in straight lines, with seeming disregard for terrain. They climb directly up steps cut on steep mesa sides and sheer cliff faces. At Pueblo Alto, several roads converge and from there descend well defined stairways to the bottom of the canyon. North of Pierre's Ruin on the North Road, four run parallel to each other only 120 feet apart. A few seem to lead nowhere. It is hard to see how this facilities commerce or the transport of crops.

Another theory holds that at least some of the roads were built for religious reasons (e.g., leading to shrines and kivas). Marshall and others suggest the roads are symbolic representations of Chacoan cosmology. Adler and others propose the idea that they were "roads through time" that symbolically linked religious features from different time periods. Others suggest that the purpose of building Chacoan roads was like that of the Roman army building roads -- discipline and unity.