Chaco Culture National Historic Park

By Edith Cherry and James See – November 27, 2022

Address:  P.O. Box 220, Nageezi, NM 87037   Map

Access: See NPS Chaco Site    Phone 505 786-7014. A Visitor Center is available.

Pueblo Bonito. Photo by Kirk Gittings.

Chaco Culture National Historical Park is an UNESCO World Heritage Site located in Northwest New Mexico. The earliest Great Houses were begun in the mid-800s AD, and all were abandoned by 1250 AD. Chaco is the most extensive pre-European architectural site north of Mexico. It was a focus for ceremonials, trade, and political activity for the Four Corners area and beyond.

People had lived in the Chaco area for many centuries in small groups. By the early 1100s, the San Juan River Basin contained around 3,200 “farming hamlets” that were the population support for Chaco Canyon.  A common pattern for these settlements was twelve rooms in two rows with a pit structure in front.  These Chacoan outliers were where most people in the area lived, and Chaco Canyon was the “center of their world.”

This discussion will not include the outliers but focus on the architecture of the seven largest Great Houses and one stand-alone Great Kiva, Casa Rinconada.  We begin with a brief description of important site features that provide context for these eight major structures.

Fajada Butte

 Fajada Butte is a landmark on southeast edge of Chaco Canyon. It rises over 300 feet from the valley floor. Three large, upright stone slabs project sun dagger images on a sandstone wall engraved with two spirals, one large and one small. These sun daggers mark the summer and winter solstices, and the spring and summer equinoxes.

Chacoans were very aware of celestial and seasonal events of many kinds. Some archaeologists believe that the locations of the Great Houses are a function of celestial alignments linking sites within the Canyon and far beyond.

Roads and Related Features

 Chaco trading and other activities required a way for people to travel on foot for many miles.  About 130 miles of roads have been verified through aerial photographs, and more than 400 miles are estimated to exist. Roads within the canyon averaged 15 feet wide while some outside the canyon were twice that. Some were bordered with mounds of earth and/or low walls as they approached public buildings. Sometimes roads were edged with herraduras (horseshoe shaped) masonry walls up to 3 feet high or aureolas, earth-mounded rings. Some roads were doubled and parallel. Stairways, massive masonry ramps and cut-and-fill indicated the extensive engineering efforts to make the roads unerringly straight over difficult terrain.

Fields and Irrigation

While the Chacoan outliers had their own fields, there were some fields in the Canyon itself and in the side valleys.  Often, they were gridded gardens where water could be poured into small garden squares with low, earthen walls.  One major field was just southeast of Chetro Ketl. The canyon also had earthen dams. The remains of one such dam, “Dune Dam,” is at the northwest end of the Canyon where Chaco Wash joins Escavada Wash to become Chaco River. Another, Weatherill’s Dam, is just southeast of Pueblo Bonito. This dam was built during the Chaco period and was later rebuilt by a farmer named Weatherill. Smaller check dams were built in the washes that feed into Chaco Wash.

Great Houses and Casa Rinconada

The buildings presented here are the seven largest Great Houses, and the largest kiva (communal, ceremonial structure) in the canyon, Casa Rinconada. Notice on the map of the canyon and the timeline below that the three oldest Great Houses are located near special geographic features: Peñasco Blanco, the westernmost site is located where Escavada Wash and Chaco Wash join to form the Chaco River. Pueblo Bonito is located where South Gap enters the Canyon. Una Vida is located where Gallo Wash enters the Canyon.  Notice also the diagrams on the timeline indicating that these three early Great Houses have a layout based on a curve, while the later houses are based on a rectangle that became a “D” shape when the south walls were added.

Common Elements of Great Houses

Construction Phases and Excavations:  The Great Houses all began as small room blocks, some of which were two stories tall. These were enlarged in a series of complex, construction episodes, most of which contributed to maintaining symmetry in the plan. We have compiled the construction phases into up to four periods of development on the timeline and site plans. Notice also that at various times between 1060 and 1125 AD, all of these Great Houses closed off their major plazas with a row of small rooms or walls suggesting a sense of completion to the Great House design.

Some of the sites have very few remains above ground. Archaeologists have studied all of these sites extensively, but some are back-filled to protect the fragile remains.

Orientation of Houses:  All but two of these houses, Peñasco Blanco and Pueblo del Arroyo, have a major courtyard open to the south. This orientation allowed for outdoor activities even in the coldest part of the winter. The major building structure to the north protected the courtyard from the cold winter wind. The two exceptions still have good winter exposure to the southeast for morning and midday sun.

Common Spaces: Major activities took place outside in the courtyards and on rooftops.  The rooms adjacent to the courtyard, and often one row back, were occupied by those who lived there, and/or conducted commercial and ritual activities at Chaco. Courtyard-facing rooms at any level would have the best ventilation. Rooms further from the courtyard were used for storage. Many, but not all, of the round rooms were used as kivas for ceremonial and community purposes. However, some round rooms were simply round rooms. Archaeologists make the determination of use according to architectural features and the artifacts found within these rooms. Also, round rooms have greater lateral stability than stand-alone rectangular rooms.

Rows of rooms that were added to back areas were often multiple stories. Rows of rectangular rooms, as well as circular rooms were added to the inner surface of houses. At various times between 1060 and 1125 AD, all of these Great Houses closed off their major plazas with a row of small rooms or walls.

Construction: The basic construction was stone foundations and walls, wood beams and lintels, and clay and sand floors. All of this construction was accomplished without metal tools. While stone was readily available in Chaco Canyon, trees for roof beams were not plentiful nearby. The nearest sources of large numbers of suitable beams were the Chuska and Zuni Mountains and Mt. Taylor, all many miles away. The trees had to be cut with stone axes and hauled, without wheeled vehicles, to the site. One should keep in mind that the making of mortar for the walls required water that was also needed for drinking and care of crops. Water for mortar was probably only available at certain times of year. 

The higher walls were tapered to be wider at the bottom where the weight is greater. Stone was shaped with stone tools, and as the Chacoans grew more experienced with masonry construction, the masonry patterns became more sophisticated. For example, later masonry walls were “core and veneer” walls, meaning the exterior surface stones were shaped, smoothed, and matched for appearance, giving the visible part of the walls a very finished appearance, while the inner stones were not. Some walls were banded with rows of a slightly darker color of stone or thinner stones. The masonry styles evolved throughout the centuries, and five major types are noted. The McElmo type is named after a valley in Southern Colorado where this style emerged about the same time as it did in Chaco Canyon, suggesting an exchange of architectural ideas.

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We will discuss each of the Great Houses in chronological order beginning with the earliest construction, and finally examine Casa Rinconada. Each site uses relatively current Google Maps overlaid with the construction periods.  These periods in all cases contain sub-phases of construction but are simplified here. Where there are no substantial ruins to photograph, we use drawings based upon archaeological data.

Una Vida

Una Vida began around 860 AD as a small, arced, cluster of six rooms and a small kiva located on higher ground than later additions. This small arc was not continued in later phases, perhaps because it was higher than adjacent buildable land. Between 875 and 925 AD, there were big functional changes that resulted in a 10-fold increase of artifacts and an “L” shaped addition of over 40 rooms. This addition, two stories in height, was to the northwest in an arced longer leg of the “L”. The west end of this addition included a three-story tower. This tower had a good view to the east up Gallo Wash and a better view to the south along Chaco Wash. The remains of this tower are the major visual features of Una Vida today; its shadow appears in the site plan. This construction period also included Great Kiva 2 in the southern part of the plaza.

The next phases added a single row of rooms to the west and inner surface of the “L”, the eastern edge of the shorter leg of the “L” and a row of rooms uphill of the original arc. The inner surface of the “L” included three small kivas.  The next construction period added the southeast wing with the back two rows of rooms at two-stories in height.  A final phase around 1095 enclosed the plaza with a row of small rooms in an arc, bringing the site up to 94,184 square feet (8,750 square meters).

Pueblo Bonito

Pueblo Bonito is probably the most well known and most studied Great House at Chaco. Centrally located in the canyon, it has a view of and can be seen from South Gap.   With almost 700 rooms, 32 Kivas,and 3 great kivas, it covers five acres (199,455 square feet: 18,530 square meters),   

The earliest construction at Pueblo Bonito was the original south-facing arc built beginning in the mid-800s AD and finishing in the mid-900s AD. The northern edge of the arc was, eventually, four to five stories high. The original inner ring of rooms is one story high, and the rooms within the arc rise up, providing usable, outdoor, south-facing spaces on the roofs of the level below. It included a variety of room sizes and a number of kivas. This configuration was a smaller arc than the final design.

The next major phase of construction between 1020 and 1050 AD built the outer ring of the multi-story north wall and several large kivas in the south plaza, as well as a number of smaller kivas.

Interior features of these two early phases include “T”-shaped doors and a corner door. The corner door is at the second level of the north wall.

Between 1050 and 1075 AD, Chacoans extended the wings of the original arc with a substantial number of rooms and at least four kivas. One of these, Kiva V, has pilasters arranged around the walls. The east wing of these additions is shown below.  Note that a collapse of the cliff face in 1941 has extended into the outer edge of these rooms.  

Final additions were made between 1075 and 1115 AD. The east and west wing additions of this period widened the breadth of the original arc and the width of each wing substantially, presenting a much larger face to the south.  Great Kiva A was built during this period, along with several smaller kivas in the east wing. The openings that remained on the south edge of Pueblo Bonito were closed off with a row of rooms that focused the entry to the west of Great Kiva A. (An additional entry to the plaza on the east side of Great Kiva A is a later change.)

Two large, horizontal platforms were developed during this period south of the south wall. These formations were originally trash mounds, but were leveled and covered with earth. These earthworks announce the south entry of the complex.

Peñasco Blanco

Peñasco Blanco is located on a mesa 300 feet above the confluence of Chaco Wash and Escavada Wash that forms the Chaco River. It is the westernmost of the Great Houses included here, and one of the few located on the south side of the Canyon. A Chacoan road passes to the south near the South Great Kiva. Peñasco Blanco’s oval shape is somewhat unusual in the area, as most houses that involve a curve are based on a section of a circle.

One of the earliest Great Houses, Peñasco Blanco began, between 900 and 915 AD, as an asymmetrical arc with three rows of rooms. The rear two rows were two stories high, making a total of about 77 rooms. The next building period, between 1050 and 1065 AD, added rooms to the east end of the arc, a row of large rooms on the inside of the west end of the arc, and Kiva G in the center. One and possibly two of the new rooms on the east end had roomwide platforms.

Between 1085 and 1090 AD, a mere five years, Peñasco Blanco grew substantially. A single row of three-story rooms was added to the rear of the arc with additional rooms on the east and west ends.  The walls of this phase were well executed, banded Type III masonry. On the interior face of the east wing, five round rooms, A through E, were added with enclosures providing a smooth face to the interior arc.

The final phase of Peñasco Blanco, 1090 to 1125 AD, included a row of rooms closing off the southeast-facing main plaza and bringing the total area up to 161,566 square feet (15,010 square meters). Apparently, parts of the center of the main building were remodeled to construct Kiva F. The construction dates for the McElmo Ruin (so-named because of its masonry style), the South Great Kiva, and Plaza Kivas 1 and 2 are not known because these structures have not been excavated. The McElmo Ruin is so-named because of its square, compact shape, a pattern that appears much further north.

Hungo Pavi 

Hungo Pavi is located at the mouth of Mockingbird Canyon. It is the smallest of the Great Houses included in this guide and houses 86,380 square feet (8,025 square meters).  The first phase, constructed between 1006 and 1010 AD, involved two rows of rooms aligned almost exactly east-west. The north two rows of the north wing were three stories high and the next row to the south was two stories high. This pueblo is based on a rectangular grid rather than the curved layouts we have visited so far. 

The second and last phase of Hungo Pavi, constructed between 1010 and 1060 AD, added the east and west wings, the curved row of rooms to the south edge of the plaza and a row of rooms to the south side of the north wing. This phase also added Kiva A and a larger kiva in the southwest quadrant of the plaza. Very little of this site has been excavated, and therefore little is known about the functions of the rectangular and circular rooms.

Chetro Ketl

Chetro Ketl is just east of Pueblo Bonito, and the two sites share a major circulatory relationship with Pueblo Alto above on the cliff to the north. A nearby stairway connected the two levels. Chetro Ketl is the largest Great House in Chaco, comprising 250,029 square feet (23,693 square meters), 500 rooms, and 16 kivas. The overall shape is that of a “D”, as are Hungo Pavi and the later Great Houses. The north wall of the “D” is angled some degrees off due north, almost parallel to the cliff face.

The north wall was over 500 feet long, and five, or perhaps six stories in places, making it the largest surface in Chaco. It is core and veneer masonry, well executed, banded in places, and made with large stone blocks alternating with several rows of smaller tablet-shaped stones. This vast wall included balconies, estimated to be about 3 feet deep. Note the horizontal groove that indicates the previous location of a balcony. They may have been used for constructing upper floors, as well as other purposes. The east wing was built in the same time phase as the north wall, between 1035 and 1050 AD. This construction phase also included two kivas to the south of the north room block.

A subsequent construction phase between 1050 and 1075 AD extended the east wing and added the west wing, which has not been excavated except for two kivas.  This addition included the Great Kiva and “The Moat”. The Great Kiva we see today is the final version of several remodels in this location. One significant change was that the plaza level was raised about 12 feet above the surrounding grade level. This effort required hauling in an enormous amount of fill dirt. The Great Kiva exhibits characteristics that we will examine later at Casa Rinconada, including an encircling masonry bench, niches in the wall above the bench, a raised masonry firebox south of the center, four pits to receive the massive roof supports, floor vaults, and a north entry chamber. “The Moat”, a term coined by the archaeologists, was built about 1075 AD and consisted to two closely spaced, parallel walls in an arc.  It was a narrow trench-like, linear space, plastered inside and out. It is not known if it was roofed.

The last construction phase at Chetro Ketl spans from 1075 to 1115 AD. This phase added a rectangular complex of rooms to the south-center of the north wing and a narrow row of rooms was added to the inside of “The Moat” which had been filled with earth when the plaza was raised. A tower kiva was added with this construction phase.

A surprising feature of the new room block was that the new south face of the north wing was a colonnade. The columns are short and squat, and rested on a low, standard Chacoan wall or sill. This feature is the only example of a colonnade in Ancestral Pueblo architecture. Such features are found In Mesoamerica, but it is not known if this idea was borrowed from Mesoamerican architecture, or developed independently here. It is known that Chacoans traded a great deal with Mesoamerican groups. The colonnade was filled in with less refined masonry prior to the abandonment of Chaco.

Pueblo Alto

Pueblo Alto began as a string of parallel rooms running east-west on top of the cliff north of Pueblo Bonito and Chetro Ketl. This phase, 1020 – 1040 AD, also included three subterranean kivas on its south side. Its location suggests that it was the first Great House encountered by visitors from the north, the vast San Juan River Basin area, and was a visible landmark on the upper plateau.  Some suggest that its purpose was to monitor access to these two Great Houses in the valley immediately below. There are more distant visual connections to Peñasco Blanco to the southwest and Una Vida upstream in the valley.

The next phase of construction, between 1040 and 1100 AD, developed the east and west wings, including two kivas in the southwest area of the plaza and a fairly large kiva in the northwest corner. A rectangular room was constructed in line with what would become the enclosure of the plaza in the last construction phase.

The final phase of construction, between 1100 and 1140 AD, enclosed the plaza with walls and rooms, and added more small kivas inside the “D” and a small room block in the west plaza. The wind-swept nature of the site has severely weathered the remaining walls. It was also during this period that the roads were developed; a few important ones touched on Pueblo Alto. The final size of Pueblo Alto was 86,380 square feet (8,025 square meters), including 120 rooms and 18 kivas. The pueblo was only one story high throughout. Domestic features found indicate that there were only about five households in permanent residence, a relatively low proportion for the Great Houses. There were special grain-milling rooms and large earth ovens suitable for preparing large quantities of food.

Pueblo del Arroyo

 

Pueblo del Arroyo is the last of the Great Houses presented in the Guide. It is the only Great House located in the valley floor. Chaco Wash’s course has deepened and moved closer to the site since it was built, threatening the ruins. While using the “D” shape of the later Great Houses, it differs by facing southeast, rather than south as do most Chaco houses, great and small. However, the plaza and rooftops still had access to a considerable amount of south sun in winter.

The first phase (1078 – 1095) establishing the orientation of the complex is the central section housing three rows of rooms and two kivas or round rooms. The rear two rows of this portion were two stories high, while the front row, facing the then plaza was one story. Some rooms on the east side had long rows of mealing bins, suggesting group efforts to produce corn meal.

The second phase (1095 – 1105) added the north and south wings and enlarged the complex considerably. The north wing has not been excavated except for the kiva. The south wing was remarkably symmetrical with the north wing, each with a large round room surrounded by smaller room blocks. These wings are believed to have been four stories, except for the three-story rooms surrounding the round rooms in the south wing.  A significant portion of the south wall of the south wing remains. A “T” shaped door can be found in this area.

The construction after 1105 made a variety of changes to Pueblo del Arroyo.  A center section was added with multiple kivas and an additional floor to the first phase rooms that faced the plaza. The plaza was also enclosed in this phase, although little of this addition shows above ground. The most unique addition, a three-ringed kiva and attendant rooms, was added to the northwest wall of the complex. No other three-ringed kivas have been found at Chaco, although they exist in the Aztec Ruins National Monument, to the north on the Animas River.

The final additions to Pueblo del Arroyo resulted in a complex of 96,767 square feet (8,990 square meters),the fourth largest at Chaco with 300 rooms, and 14 round rooms (not all are kivas).

Casa Rinconada

 The name Casa Rinconada, Spanish for “house in a corner”, refers to the nearby rock alcove. With an interior diameter of 63 feet (19.2 meters), Casa Rinconada is the largest excavated Great Kiva at Chaco Canyon and perhaps the largest in the Chacoan world. As mentioned in the description of the Chetro Ketl Great Kiva, Casa Rinconada has many of the classic features of Chacoan Great Kivas: an encircling masonry bench, niches in the wall above the bench, a raised masonry firebox south of the center, four pits to receive the massive roof supports, floor vaults, and a north entry chamber. Pottery and masonry types indicate it was built around 1100 AD, coincident with the big construction efforts at Pueblo Bonito, Chetro Ketl, and Pueblo del Arroyo. It is also fairly near these sites in what is often referred to as “Downtown Chaco.”

Casa Rinconada’s north-south axis is within one degree of true north (not to be mistaken for magnetic north). Entering the north anti-chamber on the north side, one descends steps and moves through a large “T”-shaped door to the main space. A 39-foot (11.9 meter), stone-lined sub-floor passage angles toward the west of the center of the main space. One hypothesis is that this passage allowed someone to move, undetected, perhaps also using the circular trench, and appear “center stage” for dramatic effect. Interestingly, the straight trench was filled before the last use of the kiva.

Four massive posts of Ponderosa pine (portions of a timber 2 feet in diameter were found) supported the roof. These posts rested on stacks of two to four carefully shaped sandstone disks that weighed a half-ton each. There is debate about whether the roof was ever completed prior to abandonment, but even with a partial roof, the acoustical qualities of a large, round, partially domed, room would be quite impressive.

Above the bench that circles the main space are 28 evenly spaced wall niches. Six larger wall niches, two on the east and four on the west are located lower than the smaller niches. Some researchers hypothesize that these niches are astronomical markers, but without more information on how the roof design may have permitted celestial observation, such hypotheses are difficult to confirm. Other evidence at Chaco Canyon does confirm that celestial knowledge was well established at this time. 

Epilogue

The seven Great Houses and Casa Rinconada described here, represent a total of 977,946 square feet (10,592 square meters) and are only a small part of the total amount of structures, kivas, roads, mounds, and other features built in the San Juan Basin during the Chaco Period. Yet, these structures alone represent a startling amount of work, and illustrate the architectural and engineering accomplishments of these amazingly skilled builders. Using only stone tools and lacking wheels, they accomplished feats that leave builders today in awe.  

Anthropologists may long debate if Chaco Canyon was the domain of elites or commoners, two general interpretations of the archaeological evidence. Regardless of where these debates may lead, a drought that began in AD 1130 and continued for approximately 50 years, contributed to the abandonment of Chaco Canyon and much of the lower elevation areas of the Four Corners region. Gradually, the Ancestral Puebloans left surrounding settlements and the canyon itself, quite literally, for greener pastures. They moved north, south, east and west to places with reliable streams and sufficient frost-free days to grow their corn and other crops. Their descendants are alive and well today, many continuing to honor their ancient cultures in village ceremonies throughout New Mexico and Arizona.

These massive buildings, road complexes and concentrations of exceptional effort and skill marked the culmination of a particular life way and the time for a new approach.  They present for us all cautionary tales applicable to today. There is a carrying capacity to all land. The earth is finite. Balance must be maintained. Mother Nature bats last.

Architects: Ancestral Puebloans

Contractors: Ancestral Puebloans

Awards:

ICOMOS World Heritage Site, 1987.  https://whc.unesco.org/en/list/353/

International Dark Sky Park. https://www.nps.gov/chcu/learn/nature/darkskypark.htm

Special thanks to:

Lynne Sebastian, formerly New Mexico State Archaeologist, for her review and suggestions for this article.

Kirk Gittings for permission to use his photographs of Pueblo Bonito and Pueblo Alto. They and others can be found in Shelter from the Storm: the Photographs of Kirk Gittings, Kirk Gittings, V.B. Price, Gussie Fauntleroy, New Mexico Magazine, New Mexico, 2005

Ted Jojola, Director, Indigenous Design and Planning Institute, School of Architecture and Planning, University of New Mexico for his insight, wisdom, advice, and friendship.

Learn More:

National Park Service (NPS), Chacoan Roads  

1987  Lekson, Stephen H., contributors: William B. Gillespie and Thomas C. Windes, Great Pueblo Architecture of Chaco Canyon, New Mexico, University of New Mexico Press. Albuquerque, New Mexico.

2006  Lekson, Stephen H., Editor, The Archaeology of Chaco Canyon, School of American Research Press, Santa Fe, New Mexico.

2007  Lekson, Stephen H., Editor, The Architecture of Chaco Canyon, New Mexico, University of Utah Press, Salt Lake City, Utah.

2012  Vivain, R. Gwinn and Hilpert, Bruce, The Chaco Handbook, An Encyclopedic Guide, Second Edition, University of Utah Press, Salt Lake City, Utah.

11/27/22