Pueblo Bonito is the best-known of the great house sites in Chaco Canyon, among the most fully excavated, and by at least some measures the biggest. Even from a distance, such as from the parking lot from which one approaches it, it looks massive and imposing. As, indeed, it is, and it is in mass (number of rooms, amount of masonry, etc.) that it claims the title of largest great house. In area Chetro Ketl, another great house right next to Pueblo Bonito, is actually slightly larger. But it is Pueblo Bonito that has claimed the greatest amount of publicity, for a number of reasons, some better than others.
Part of the way down the trail from the parking lot to Pueblo Bonito is a plaque that has an artist’s rendition of how the building may have looked at its height around AD 1100. Although there is inevitably a bit of artistic license in reconstructions like this, this particular one is about as accurate as they get given the information available, and it is actually a modification of an earlier rendition taking into account newer research. One thing that can be seen from this image is the sheer size of Pueblo Bonito. The little people running around the building are to scale, which shows that this was a very large building indeed in its time.
Another thing that can be seen from the artist’s rendition, and perhaps more clearly from the architectural plan view next to it on the plaque, is something of the shape of Pueblo Bonito. One aspect of the layout that is particularly notable is that there are a lot of straight lines, right angles, and abstract geometrical forms, culminating in the overall D-shape of the entire building. This regularity is clear evidence that there was a considerable amount of planning involved in the design of Pueblo Bonito. This is typical of Chacoan great houses, many of which show even more regularity in design than Pueblo Bonito, but it is actually not typical of Pueblo sites in general. Most Pueblo sites both before and after the Chacoan era (ca. AD 1030 to 1130) show a very different pattern of development, a more functional, organic pattern with one room being added onto another as necessity dictated, with no particular attention being paid to the overall form of the building. This type of development is typical not only of early sites, but also of sites after the Chacoan era, including the famous cliff dwellings at Mesa Verde, Canyon de Chelly, and Navajo National Monument, which are large and impressive, to be sure, but not particularly planned.
And, indeed, even during the Chacoan era, and even right in Chaco Canyon, we see a very different type of site from the great houses, most of which are on the north side of the canyon. On the south side of the canyon across from Pueblo Bonito, near the great kiva Casa Rinconada, are a few sites that have been excavated and stabilized which show a very different pattern of development from the great houses, a pattern much more typical of other sites from other times and places. They don’t show the large scale, planned nature, and elaborate construction techniques that distinguish Chacoan great houses from other Pueblo sites. These are called “small houses” in contrast to the great houses, and they actually line the canyon from one end to the other, mostly on the south side. Indeed, there are many more of them than there are great houses, and from tree ring dates we know that they were being built and occupied at the exact same time, and it is now thought that the vast majority of people in the canyon at the time lived in the small houses.
This leaves us with a bit of a mystery. Why were there two very different types of sites being built and used in the same place at the same time?
It’s actually an unsolved mystery, and only one of many such mysteries about Chaco Canyon. Most of these mysteries center on the great houses, which remain puzzling in many ways despite having been intensively studied for over a hundred years. That century of research has resulted in some answers to be sure, but it has raised at least as many questions. There are things that we do know. We know a lot about when they were constructed and how they were constructed, but we know very little about why they were constructed and what their function was, and indeed what was going on that made Chaco such an important place in its time. These are, of course, many of the most interesting things about the great houses, and the things we might most like to know. Many theories have been proposed to bridge the gap between what we know and what we would like to know, but they’re all based on the same rather meager evidence, supplemented with a considerable amount of speculation, and as a result they conflict quite a bit. Thus, in the remainder of this post I will be focusing mostly on the things we do know from the archaeological record, which are the building blocks out of which the theories are constructed, and leaving the theorizing to my readers, since, to a remarkable degree, your guess is as good as anyone’s about what was going on in Chaco.
The southeast corner of Pueblo Bonito is a good place to see the fine masonry for which Chaco is justly famous. Most of the stonework visible here is original; the mortar is not. You can see various types of mortar here, including some Portland cement, some other types of cement, and some mud. The original mortar was mud-based, and it held the walls together fine while the building was being used and maintained. Then, over the hundreds of years during which the building was no longer in use and was gradually being filled with windblown sand, the sand kept the walls stable and standing remarkably well. So well, in fact, that not only were the walls preserved, the contents of the rooms they formed were preserved remarkably well, and when they were eventually excavated the excavators found an astonishing variety of artifacts, including many made from perishable materials that don’t typically survive so long. Once the building was excavated, however, and the walls were exposed to the wind and rain they began to deteriorate pretty rapidly, and one of the first things to go was the mud mortar when it was exposed to the wind and rain. Thus, the park now has a full-time preservation crew that goes around to each of the buildings and does whatever it takes to keep them standing. One of the main things they do is touch up the mortar, typically by pushing new mortar into the spaces where the original has fallen out (rather than by redoing the stonework entirely). Early on they used Portland cement, but over the years understandings of material properties have improved and it is now known that Portland cement is not a good material to use for this, for a variety of reasons not least of which is that it has different properties from the original mud, which remains in significant quantities inside the thick walls. One of the most important differences is the rate at which the materials expand and contract during annual freeze-thaw cycles, with the result that different parts of the walls end up moving at different rates over the course of the year, which actually tends to destabilize the walls a bit. Thus, the preservation crew at Chaco has moved toward other types of cement that mimic the behavior of the mud more, as well as mud, which mimics the behavior of the mud exactly, but one of the ways in which it does so is that it falls out easily and has to be replaced a lot. What material to use in each situation is a judgment call to some extent, and the crew makes different decisions in different places.
Another thing the preservation crew does is capping. The top foot or so of every wall is modern capping, which is done in the same style as the original masonry but often using a slightly different color of sandstone. This can be seen clearly in some parts of the southeast corner of Pueblo Bonito, including the part in the picture above, where the reddish sandstone is original and the lighter sandstone toward the outside of the wall is the capping. This capping is done to stabilize the walls and keep them from falling down, which is a constant risk when they are exposed. Again, early on they used Portland cement for this, but more recently they’ve shifted to other types of cement that work better in context. You can’t really use mud for this, because the important thing is that it stay on. You don’t want any risk of that capping coming off or the walls will fall down.
Continuing on from the southeast corner, one comes to an overlook from which (almost) the entirety of Pueblo Bonito is visible. Many things are visible from here, one of which is that the part of the building that is visible from the parking lot and the trail leading from there toward the building is just the southeast corner; the entire building extends considerably further to the west.
This overlook was not always there. It was built atop the remains of a big rock that fell on Pueblo Bonito on January 22, 1941. This rock was called “Threatening Rock,” and the name was apt. It looked somewhat like another rock that still leans out over the canyon floor just east of Pueblo Bonito, visible from the overlook, but it was about four times as big.
When it fell, Threatening Rock crushed about thirty rooms of Pueblo Bonito that had already been excavated, but it also provided the Park Service with a nice little overlook, so there was at least a bit of a silver lining. The amount of fallen rock still in place is impressive, particularly when one considers that it was all originally a single rock.
On top of the overlook there is a nice plaque that illustrates the various construction stages of Pueblo Bonito. The building wasn’t built all at once, but in a series of construction stages over the course of about 300 years. The first stage, starting around AD 850 and continuing through the 930s, was an arc of rooms with an open plaza in the middle containing some kivas. This was not an unusual layout for a Pueblo site of this period, and this part of Pueblo Bonito is notably less regular than later parts. Pueblo Bonito was, however, pretty distinctive even at this early date, in that it was much larger than other Pueblo sites. The rooms were much larger than in other sites, and the building was three stories tall in places, whereas other buildings in the region were at most one story tall in this period.
Once the first stage of construction was complete, the building remained more or less the same for the next hundred years. Then, in the 1040s, as the Chacoan era was beginning and the Chaco system was gearing up, a lot of changes took place in the canyon, and among those was the expansion of Pueblo Bonito. This expansion took the form of the wings of the arc being extended and the plaza being enclosed by a straight wall on the south side, forming for the first time the D-shape and enclosed plaza that became hallmarks of the Chacoan great-house style of architecture.
Once that stage was complete, the Chacoans just kept building, with extensions and expansions coming fast apace for the next hundred years in a confusing welter of changes that are very difficult for us to untangle. By the early 1100s it had reached more or less the final state that we see today.
Another thing that is quite noticeable from atop the Threatening Rock overlook is that Pueblo Bonito is not the only building in its immediate vicinity. Indeed, there are buildings all around it: Pueblo del Arroyo, just to the west; Kin Kletso, a little further west at the foot of the cliff; Chetro Ketl, across a flat area to the east; Casa Rinconada, across the canyon to the south; and the small house sites, which do line the canyon from one end to the other but are particularly concentrated in this area around Casa Rinconada and across from Pueblo Bonito.
A considerable amount of architecture, then, all around Pueblo Bonito. And it’s not just architecture, either; there are also roads, mounds, flattened open areas, and various other types of landscaping tying the buildings all together. This, then, is not just a group of unrelated buildings separated by stretches of untamed vegetation, as it looks today. At the time it was developed, this was a deliberate effort at putting together a large-scale arrangement of buildings and landscaping. It is interesting to note that, except for a few of the small houses, all of these other buildings were built after Pueblo Bonito had been there for quite some time, mostly in the period when Pueblo Bonito was being expanded. This, then, may lead us to wonder why Pueblo Bonito was put where it is in the first place. (It may also lead us to wonder why any of this is in Chaco Canyon in the first place, which is a considerably harder question to answer.)
Within the canyon, however, this is a pretty good place to put a big, important building, and that’s because of something else that can be seen from the Threatening Rock overlook: South Gap, one of the three main gaps in Chacra Mesa to the south that provide the three main entrances to Chaco Canyon. These three entrance points are South Gap, Fajada Gap to the east where Fajada Butte and the current park visitor center are, and the point to the west where the Escavada Wash comes in from the north and joins with the Chaco Wash to form what is called the Chaco River (which is still a wash). It is at these three entrance points where we find the three earliest great houses, each built around the same time, with the same construction style, similar layouts and similar sizes: Pueblo Bonito at South Gap, Una Vida at Fajada Gap, and Peñasco Blanco where the Chaco and Escavada Washes come together. Over the next two hundred years all three of these great houses were expanded considerably and had other buildings built around them, but Pueblo Bonito was expanded considerably more than the other two and had much more built around it. In this connection, it is interesting to note that South Gap is the central of the three entrance points. This part of the canyon, then, was the center. It is an area that archaeologists today often call “Downtown Chaco,” which I think is a good way to think about it. Pueblo Bonito, in turn, is the center of Downtown Chaco, which is the center of the canyon, which is the center of the Chacoan world. It is the center place, the most important of all the great houses, and thus the one that is the most frequently visited and toured, as well as the subject of this virtual tour.
Moving along the back wall of Pueblo Bonito and inside the building, one comes to the oldest part, unimaginatively called “Old Bonito.” This is the original arc of rooms built beginning around the AD 850s and continuing up to around the 930s. One of the most striking things about the remains of this early building stage is the masonry, which is quite different from the later, better-known Chacoan masonry. The difference can be seen in many places in and around Old Bonito where early and late masonry are both present.
This early masonry, known as “simple” or “Type I” masonry, basically consists of unshaped sandstone slabs laid together with a lot of mortar then plastered over on both sides with a mud plaster. It works well enough, and with the size of rooms used in Old Bonito the Chacoans were able to go up three stories with it, and for the hundred years when that was the whole building it stood acceptably (though some have argued that it was not very stable at that height). When the building was expanded in the 1040s, however, it was expanded not only out but up, with high-ceilinged rooms going up three, four, and possibly even five stories in the back. For that scale of building, the Type I masonry was not going to work; it’s just not strong enough.
To deal with this problem, the Chacoans invented a new type of stronger masonry that would become closely identified with Chacoan great-house architecture over the course of the Chacoan era. We call this “core-and-veneer” masonry, and it is basically composed of two parts: a core of rubble and unshaped sandstone blocks, laid together with mortar, and a structural veneer of sandstone blocks that are left rough on one side and hooked in with the core blocks and finely shaped on the other side and laid in elaborate patterns and courses, the styles of which change over time and provide a rough dating system for different parts of buildings. This veneer was then plastered over, just as the earlier Type I masonry had been, so it would not actually have been possible at the time to see the fine stonework that we today find so impressive about Chacoan masonry.
The advantage of this core-and-veneer style from a structural perspective is that you can make that core as thick as you want just by putting in more rubble and blocks and then slapping on the veneer; the core and the veneer support each other. That is, you’re not limited by the size of the stones you happen to have, as you are for the simple masonry. Thus, this type of masonry can be used to make very thick walls, and that’s exactly what it was used for. The back walls of Pueblo Bonito are built thick enough at the base to support five stories. We only see remnants of four stories, but some archaeologists think there was a fifth story in some places, because the walls could support it. They taper as the go up, to reduce the load on the lower walls. All in all, a very sophistocated style of construction, particularly given the technology being used for it.
However, another thing that can be clearly seen in Old Bonito is that the Chacoans did not tear down the part of the building built with the older, weaker type of masonry when they developed the newer, stronger type. Instead they encased it within the newer walls. Whether this was intended to protect the older part of the building is one of those things that are impossible for us to know for sure, but it certainly did protect large portions of Old Bonito, preserving them well enough that we can see substantial parts still standing today. This seems to indicate that the older part of the building continued to be important even after the expansions that transformed Pueblo Bonito into a much larger and somewhat different structure.
There are other things about Old Bonito that indicate its continuing importance, particularly the artifacts that were found there. In addition to being the oldest part of the building, this was one of the first parts to be excavated. When it was excavated, the excavators found some truly remarkable artifacts, in both quantity and quality, in some of the rooms. Many of the rooms contained hundreds or even thousands of elaborate, valuable artifacts, most of which seem to have been ceremonial in function (prayer sticks, cylinder jars, etc.), just lying there. These were apparently caches of ritual objects, though the exact reason the objects were being cached remains mysterious. The sheer quantity of them, however, indicates that whatever the purpose, it was strongly identified with this particular part of Pueblo Bonito. Nothing similar was found anywhere else in Pueblo Bonito, or indeed elsewhere in the canyon.
Another type of evidence for the continued importance of Old Bonito, also found by the early excavators, was burials. Surprisingly few burials were found in Pueblo Bonito overall, given its size and the assumption, generally held by the excavators, that it was a large residential community comparable to modern pueblos. About 130 burials were found total throughout the building, which is not a trivial number, to be sure, but considerably less than would be expected in a site with at least 600 rooms occupied for over 300 years. This puzzled the early excavators, who went around looking in vain for outside cemeteries. Today it’s widely thought that this probably just indicates that there were never very many people actually living at Pueblo Bonito or the other great houses; that is, while they do show some evidence of residential use, for most of their occupation they were not primarily residential in function.
In any case, those 130 burials in Pueblo Bonito were mostly concentrated in just two parts of the building, both of which are in Old Bonito. One part was a block of four rooms at the far west end of the arc, and the other was another block of four rooms at the north end, the top of the arc. These burials were, in comparison to typical Pueblo burials at the time, even in the small houses right across the canyon, odd. Typical Pueblo burials, such as the ones at the Chaco small houses, have few if any grave goods. A typical grave assemblage would have perhaps a bowl or two, and in rare cases an ornament or other valuable object. The assemblages at Pueblo Bonito, however, went far beyond that. What is particularly interesting in addition to the atypically elaborate grave goods is that there was a marked difference between the two burial groups even within Pueblo Bonito. The ones in the western section had considerably more grave goods than was typical, with the goods being primarily pottery, ornaments, and objects of daily use, found in fairly large quantities but also with a relatively large number of people buried in each room, so the average number of grave goods per burial is fairly low. The burials in the northern section, however, were unbelievably lavish even compared to the western ones. While there was a considerable amount of pottery and various other goods in these rooms, the thing that really makes them stand out is the number of ornaments. One room alone in this section had over 65,000 pieces of turquoise in it, several orders of magnitude greater than any other find elsewhere in the canyon or even, at least to my knowledge, elsewhere in the prehistoric southwest. Most of these pieces were little beads, of course, but still, that’s a lot of little beads. There were also considerably fewer people buried in these rooms, raising the number of goods, particularly ornaments, per person to incredible heights. It’s not at all clear who these people were or why they were buried so lavishly, and theories and opinions among scholars are bitterly divided over the question, but it is clear that whoever they were, they were pretty important, and the place where they were buried, Pueblo Bonito, and more specifically, Old Bonito, was pretty important as well.
Moving from Old Bonito into the plaza, one of the first things one sees is a great kiva. Generally thought to have been primarily ceremonial in function, comparable to kivas at modern pueblos, great kivas are a typical feature of Chacoan great houses, and they are typically found either in the plaza, as here, or just outside of the great house. One of the fascinating things about Chacoan great kivas specifically (there are other kinds) is their standardization. The same set of features is found with very limited variation throughout the Chacoan world, which encompasses the whole San Juan basin and a considerable area beyond. This one, called Kiva Q, is one of the earliest known examples of a Chacoan great kiva, but it already shows the standard set of features.
Among the features that can be seen in this great kiva are the encircling bench, the central fire box, and the four circular masonry structures arranged in a square that served as postholes for the large trunks of ponderosa pine that held up the roof. An intact great kiva roof has never been found, so there isn’t 100% agreement about how roofs were designed and constructed, but enough fallen timbers from the roof are typically found inside that we can get a rough idea. It’s generally thought that the roof was flat, with the tops of the posts connected by beams to form a square, and timbers radiating out from that square to form a flat ceiling from the inside and a flat roof, covered with mud and packed earth, from the outside. It is generally thought that there was a smokehole over the fire, and many think that there was a ladder through the smokehole providing access to the great kiva, as is typical at smaller kivas, where this ladder is the only entrance to the kiva.
Great kivas, however, always have at least one other entrance, so not everyone is convinced of the ladder theory. This entrance is always either at the north end or the south end (in Kiva Q it is at the south end, while at Casa Rinconada, the largest great kiva in Chaco Canyon, there is one at each end), and it consists of masonry steps leading down from an antechamber. In Kiva Q the steps only go partway down, and there was presumably a ladder connecting the end of the steps to the floor of the kiva. This entrance also provided ventilation, and to keep the incoming air from blowing out the fire there is a deflector, which in this case is a grooved masonry structure (unfortunately not really visible in my pictures) that would have held up wooden boards to direct the airflow around the room rather than straight onto the fire.
In addition to those more obvious, structural features of great kivas, there are some other standard features that are a bit more mysterious. Among them, also unfortunately not visible in my pictures of Kiva Q, are small holes going partway through the wall that we call wall niches. In Kiva Q there are just four of these and they are at the north end; in many other great kivas, including Casa Rinconada, there are about 30 and they go all the way around. Their function is not clear. They are sometimes found with ornaments or bits of turquoise in them, either placed in them or sealed into them, but more frequently there is nothing in them. In Casa Rinconada some of them seem to have astronomical alignments, but this doesn’t seem to be the case at Pueblo Bonito. Whatever they were for, they are always there.
Another mysterious but typical feature of Chacoan great kivas is the presence of two rectangular masonry structures between the postholes on either side of the firebox. These are called “vaults” and their function is unknown. Some have proposed that they were footdrums, with boards laid over them and people dancing on top to provide percussion for the events in the kiva; others have proposed other functions, such as sweatlodges, places for germinating seeds or beans (which is something the Hopis do in their kivas today), etc. In any case, another very standard feature of the Chacoan great kiva design, which is an indication of the amount of thought and planning that went into the elaborate region-wide Chacoan system, whatever it was.
Turning from Kiva Q to the plaza, it becomes apparent that there are actually two plazas, separated by a block of rooms. Moving south along the wall of this block of rooms, one comes to another block of rooms, enclosing the plazas on the south side and forming the straight side of the famous D-shape. Where these two blocks of rooms intersect, there is a doorway.
At the time this part of the building was completed, sometime in the early 1100s, this doorway was the only entrance to the building. To get to any of the interior rooms, you would have had to enter here, go across the plaza, possibly go across the other plaza, then make your way through a maze of interconnected rooms. It was not easy to get to many parts of this building. Clearly an attempt to limit access, but why? The early excavators assumed features like this were defensive in nature, but research has actually shown that there is very little evidence of warfare during the Chacoan era. Indeed, it seems to have been a very peaceful time, particularly in comparison to the eras before and after it. So probably not defensive, but still limited access, and the reasons for that are answered in different ways by the different theories about the function(s) of the great houses and the nature of the Chacoan system.
There is, however, something else meaningful about this particular spot. The aforementioned wall dividing the two plazas runs due north-south, within a degree of true north, and the wall enclosing the west plaza runs due east-west, again within a degree, and they come together in a 90-degree angle right here at the only entrance to the building. This is clear evidence that, at least at this late date in the history of Pueblo Bonito, alignments were very important elements of the Chacoan architectural style. This is a particularly clear example of cardinal direction alignments; there are also astronomical alignments at many buildings, as well as alignments between buildings. This, along with the roads, the line-of-site communication network, and the various other landscaping and engineering projects throughout the Chacoan world, shows that the Chacoan system of architecture didn’t end at the walls of the building or even at the walls of the canyon. Rather, it extended out, through roads and other networks to the surrounding region, and through abstract alignments to the cosmos itself and the movements of the sun and moon. A very sophistocated and impressive system indeed.
A system this elaborate obviously required a lot of work to build and maintain. From the impressive remains of it, it is clear that this work was done, and it seems like there must have been something, some idea or system of ideas, that was powerful enough to inspire someone to either do this work or get other people to do it. Though we see some tantalizing glimpses and possibilities in the architecture and other remnants, ultimately we don’t know what that idea was. We can’t see just what it was that inspired the creation of all this magnificent construction and design that, in turn, inspires us today. There are theories, but none of them can really claim to have the whole answer, at least not in a way that will be universally accepted. There are still many things we don’t know and will never know about Chaco.
That’s not necessarily a bad thing. In some ways it can be a benefit to not know and to be able to ponder, think, and consider the possibilities and limitations inherent in the human experience, and I think Chaco offers that opportunity and that, to us today, that is a key (and, in any case, necessary) aspect of how we approach Chaco Canyon and Pueblo Bonito at the heart of it. It’s a place of majesty and a place of mystery.