Pueblo del Arroyo, the latest and smallest of the large “Bonito-style” great houses in Chaco Canyon, is an interesting site for a variety of reasons. It occupies a transitional place in the history of the canyon, both between the Bonito phase and the succeeding McElmo phase and between the era of the Chaco system as a whole and whatever it was that succeeded it. Although it was built later than many other large sites in the canyon, and thus had a shorter period of overall occupation, it still shows a considerable amount of change over time that illustrates larger-scale changes that are not as visible at the older, more complicated sites such as Pueblo Bonito.
The northwest corner of Pueblo del Arroyo is the first part of the site one reaches when walking up from the parking lot. This part of the site, the north wing, is unexcavated, and it offers a good opportunity to see what the rest of the sites looked like before excavation. There are a considerable number of standing walls, showing the overall size and shape of the building, but most of the lower stories, especially the first story, are still mounded over with windblown sand. This sand, which filled in the lower stories which were protected by thick walls and prevented from falling down like the upper stories, still protects whatever lies inside these rooms in the north wing. We don’t know what is in them, but judging from what was found in the rooms elsewhere that have been excavated, it’s probably pretty impressive and well-preserved. This sand, which protects the contents of the rooms very well, is one of the things that makes Chaco such a well-known and spectacular place: in addition to the fineness of the architecture, the artifacts preserved by the sand are quite impressive as well.
Moving along the west wall of the site and up into the north wing, one can see pretty much the whole site. In contrast to the larger sites like Pueblo Bonito, Pueblo del Arroyo is a lot easier to get a handle on. It’s small enough for the whole thing to be readily visible from the upper parts of the north and south wings.
The earliest construction stage at Pueblo del Arroyo took place between around 1065 and 1075 AD. This was the back portion of the central roomblock, starting with the west wall. It was three rows wide and approximately the same length as the final central roomblock, although some parts may have been covered over by later construction of the wings.
Later, between about 1095 and 1105 AD, two wings were added to this roomblock, one on the north side and one on the south side. These are pretty similar to each other, although they differ in a few ways. They both consist of one or two central elevated round rooms surrounded by rectangular rooms to form an overall rectangular shape.
The north wing, which originally went up three stories, has two round rooms at its center, one on the second-story level and one on the third. The one on the third story has been excavated and is the only part of the north wing to be excavated. It is a good example of a “Chacoan” style round room (or “kiva”), with an encircling bench containing several pilasters, cube-shaped masonry blocks with radial logs inside them. The function of the logs is obscure, but the pilasters as a whole served as bases for the logs that were laid across them and then built up to form a cribbed roof, sort of a false dome with a smoke hole in the center that also provided access to the room via ladder. As the presence of a smoke hole implies, there was also a hearth on the floor of the room (now covered up in this case, like the other floor features, by backfill). On the south end of the room is a vent shaft, which brought in air from outside and could open either at the level of the bench or through the floor.
In addition to the internal features, the main thing that distinguishes “Chacoan” round rooms from others is their positioning within the site. Unlike many other round rooms, which are subterranean or semi-subterranean, these rooms built above-grade into the square roomblocks around them. This is a distinctive feature of Chacoan sites, but it’s pretty mysterious. It’s totally impractical structurally, as it creates four small corner rooms that are generally pretty useless and, indeed, are usually used to buttress the round room, either with logs set across them or by being filled in entirely. Whatever the purpose of the blocking-in, however, it is a typical feature of Chacoan sites.
Another more unusual feature of this particular round room can be seen where the fill has been cut away to reveal a lower level of masonry below the main bench level. This masonry is quite different from the fine “Bonito-style” masonry above it, which uses the hard, tabular sandstone quarried on top of the mesas that is typical of the masonry in Bonito phase great houses. Instead, it is made of larger blocks of the soft, yellowish sandstone found at the base of the cliffs. It resembles the “McElmo-style” masonry seen in the construction of sites such as Kin Kletso, which is quite close to Pueblo del Arroyo and visible from the north roomblock. These sites seem to have been built in the early 1100s, toward the end of the Chaco era, and their style is therefore generally thought of as later than the “classic” Bonito style. Pueblo del Arroyo, however, was built over a period that seems to been transitional between the two styles, and the north roomblock especially shows several places where Bonito-style and McElmo-style masonry seem to have been used at the same time, often, as in this round room, with the “later” McElmo masonry below the “earlier” Bonito masonry, clearly showing that McElmo masonry is not necessarily later than Bonito masonry at all. Explaining this is difficult, and Pueblo del Arroyo seems to be the only site that shows this sort of thing on this scale.
The south wing, unlike the north, has only a single blocked-in round room at its center, at the second-story level. This room is larger than either of the two round rooms in the north wing, but it is otherwise pretty similar to the excavated one there. The south wing as a whole is also pretty similar to the north wing, except that it went up four stories instead of three. Both wings consist of a very regular pattern of square rooms surrounding one or two round rooms, which is a pattern very similar to that seen in the later McElmo sites, which are very regular and modular and tend to be made of one or more “units” consisting of one or two round rooms surrounded by square rooms. (Most McElmo sites have one of these units; Kin Kletso has two.)
The two wings of Pueblo del Arroyo, then, both built around 1100, are strikingly similar in plan to the McElmo units of a few years later. They are generally still made of Bonito-style masonry (although note what I said above about the overlap in styles), but otherwise seem to be precursors of the later sites. Again, hard to explain, but seemingly unique to this transitional site.
Another difference between the north and south wings is that the south wing has been excavated, so it is possible to look down from the level of the elevated round room and see quite a bit of the lower stories. They have been refilled to varying levels, but there is still quite a bit to see, including, in one room, some of the original roof beams showing the style of roofing, which consisted of large beams of ponderosa pine spanning the short axis of the room, crossed perpendicularly above by smaller beams of aspen or other small trees, then covered with juniper splints which sealed in the packed earth that formed the floor of the room above.
The next stages of construction are harder to date, but they seem to have taken place sometime in the early 1100s. They are the expansion of the central room block eastward toward the plaza, with the new construction consisting largely of blocked-in round rooms at various levels, and the final enclosure of the plaza within a one-story arc of rooms, forming an overall D-shape to the building. This shape is quite common for Bonito phase great houses, and it is seen in Chetro Ketl, Pueblo Alto, Hungo Pavi, and a variety of other sites as well. Interestingly, the sequence of construction of all these sites seems to have been the same as well, starting with the central roomblock, followed by the two wings, then finishing with the enclosing arc of rooms. This is the case even though the sites were all begun and finished at different times, which implies that they may all have been planned with the final shape in mind from the very beginning.
Despite its rather typical shape and sequence of construction, however, Pueblo del Arroyo is unlike any other great house in the canyon in its positioning and orientation. While most of the great houses are at the foot of the cliffs on the north side of the canyon and face south, with their highest levels on the north side and the rooms terracing down from there to the enclosed plaza on the south, Pueblo del Arroyo is out in the middle of the canyon, right next to the Chaco Wash (hence its name), and it faces east, with its long, straight back wall with the highest stories on the west side and the enclosed plaza on the east. This is very difficult to explain. It could have something to do with its late date, but it’s clearly not the case that there was no room left on the north side of the canyon at the time Pueblo del Arroyo was initially constructed, since Kin Kletso, which was constructed even later, is right at the foot of the cliff quite close to the site of Pueblo del Arroyo.
One reason Pueblo del Arroyo might have been placed as it was is apparent from a look at the south side of the building, which is interesting for many reasons. Like many exterior walls of great houses, this one has no doorways on the first floor but does have several doorways on the second floor (and probably on the third and fourth, which have not survived high enough to tell). Some of these doorways are T-shaped, an unusual and probably significant shape that has been proposed as a sign of Mesoamerican influence, while others are more typical rectangles. It may seem a bit odd to have doorways on the upper stories when there are none at ground level, but the reason is actually fairly clear from evidence at other sites such as Chetro Ketl, where there were balconies at the floor levels of the second and third stories on the outside of the building. Although there is no direct surviving evidence for balconies at Pueblo del Arroyo, it is reasonable to conclude that there were originally balconies and that the upper doorways didn’t serve as entrance points to the building but as exit points from the building to the balconies.
If there were balconies on the south side, though (which, remember, is not the front of the building), what were they there for? What would people see when they walked out onto the balconies?
The answer is clear from turning around and looking south, where a couple of potentially important things are clearly visible. The first, of course, is the wash, which runs right next to Pueblo del Arroyo. Keeping an eye on the water flow would be a useful thing to do, for obvious reasons. The second is perhaps a bit less obvious in its importance, but it’s at least as striking in its effect. This is the large gap in the mesa to the south directly across from Pueblo del Arroyo.
This gap, called South Gap, was one of the three main entrance points to the canyon from the south, and it makes sense that having a building overlooking it would be useful both for monitoring who and what was coming in and for impressing people entering the canyon with the monumental nature of the building. The early great houses built in the 800s, Pueblo Bonito, Una Vida, and Peñasco Blanco, are all built at or near the gaps (respectively: South Gap, Fajada Gap, and the point to the west where the mesa ends, which is not really a gap but is still an entrance point to the canyon), but Pueblo Bonito is not actually directly across from South Gap. Pueblo del Arroyo is. It is hard to escape the conclusion that the odd siting and orientation of Pueblo del Arroyo likely had something to do with this.
There’s another odd thing about the south side of Pueblo del Arroyo. When the south wing was initially constructed, the second, third, and fourth stories of the southernmost row part of the addition were constructed as usual, with long walls subdivided by cross-walls to form a series of rooms. On the first story, however, there were no cross-walls. The whole thing formed one extremely long, continuous room. As a result, the weight of the upper stories was not adequately supported, and the wall began to lean outward. To stabilize it the builders put up a series of buttresses on the outside, which seem to have worked, and the wall is still standing and in fairly good condition today.
Much later (although it’s impossible to say exactly when), someone (it’s impossible to say exactly who) came along and turned these buttresses into the cross-walls for a series of rooms built along the south wall of Pueblo del Arroyo using very crude masonry. These rooms show lots of evidence of residential use, so we do know what the people were doing in them, but beyond that it’s very difficult to say why they built them. They do seem to have used at least some rooms inside Pueblo del Arroyo as well, so it wasn’t that they didn’t have access to the building. This was likely long after the fall of the Chaco system, probably in the late 1100s or even later, and it’s a good example of the changes that took place in the canyon after the end of its regional importance. For some reason these changes are much more apparent here at Pueblo del Arroyo than at other sites.
Walking around the southwest corner of the building, one can see just how close the wash comes to the building. There are a variety of erosion-control devices visible to keep the wash from eating away at the building any more than it already has. There are also many preservation measures apparent to drain water away from the building and into the wash, most notably a downspout and pipe that the preservation crew painted to blend in with the surrounding masonry. It’s one of their more whimsical efforts.
Perhaps the most spectacular example of the post-Chacoan changes at Chaco that can be seen at Pueblo del Arroyo is on the west side. Built right against the back wall of the building is a remarkable and mysterious structure built of three concentric circular masonry walls, with the two outer rings divided into rooms by radial walls. The masonry style indicates that at least most of this structure is clearly later than the rest of the building, being more like the classic McElmo style of the early to mid-1100s.
This is an example of what is known as a “tri-wall structure.” It’s the only one at Chaco, but not the only one anywhere. They are mostly associated with the area to the north of Chaco, which was rising in importance regionally during the 1100s at the same time that Chaco was declining. There are tri-walls in the Mesa Verde area, and they are particularly associated with the Totah area along the middle San Juan river valley. There are at least three of them at Aztec Ruins, which seems to have become a major regional center around this time. This one at Pueblo del Arroyo, then, seems to indicate influence from the north in the post-Chaco area, although beyond that it’s hard to say much about it. It has been excavated (and later backfilled for preservation), but the excavations found that it had been substantially dismantled in antiquity, apparently for building stone. It’s not clear where the stone was used, but the row of rooms along the south side of Pueblo del Arroyo is one obvious possibility.
Because of the disassembly, not much was left to indicate the function of the tri-wall. Despite its round shape, however, it bears little resemblance to other round rooms such as great kivas. Most other round rooms of whatever size and shape have hearths in the center, but the tri-wall doesn’t. Instead, the innermost circle has a flagstone floor. This is a very unusual feature, as rooms in these sites almost always have earthen floors, but it is known from some other sites where it seems to be a functional aspect of storage rooms used to keep rodents out. Here, however, it likely has some more esoteric purpose.
The prevalence of tri-wall structures throughout the San Juan basin during the 1100s, and their absence before and after, seems to indicate that they were associated with a short-lived flourishing in the immediate post-Chaco era of some sort of regional social or ceremonial system, possibly centered on Aztec. Since it was so short-lived, however, and no aspect of it seems to have survived in recognizable form into the present-day Pueblos, it is perhaps even harder to interpret than the Chacoan system that it seems to have replaced.
Coming back around from the tri-wall to the northwest corner, one has circled the entire building. It is notable that the tri-wall, one of the later, mysterious additions that make Pueblo del Arroyo so interesting, is right up against the west wall, the earliest part of the building, which in a sense brings things full circle. Despite its relatively short period of occupation, Pueblo del Arroyo shows a lot of change and mystery, which makes it a fascinating place deserving of much more attention than it usually gets.