Returning to my theory that the large square rooms with hearths and other residential features found at some great houses in Chaco and elsewhere were in some sense replacements for earlier kivas, I think the best evidence for this at Chaco itself (as opposed to at outlying great houses like Salmon) comes not from Pueblo Bonito, which is just too complicated a palimpsest to make something like this easy to see, but from the other early great houses: Una Vida and Peñasco Blanco. These at least seem to have simpler layouts than Bonito, though the extent to which this is just an effect of their being (mostly) unexcavated is unclear. Nevertheless, at least some parts of these two great houses do seem to show basically the pattern that I’m proposing for the development of residential room suites at great houses.
To recap the idea: The very earliest great houses, those built in the AD 800s, seem to show a pattern of suites similar to that seen at small houses or unit pueblos, with each suite consisting of one rectangular room backed by two smaller rooms. In front of each roomblock there are subterranean kivas, usually with slightly fewer than would be expected if each suite had its own kiva. This suggests to me that the suites housed individual nuclear families, but that they were grouped into larger units, perhaps extended families, which shared kivas. Whatever rituals these residential units would have conducted would probably have been in the kivas, but for the most part these were still residential structures, similar to the pithouses occupied in earlier centuries but with some of their functions transferred to the rectangular front rooms of the roomblocks. The smaller rooms in the back would have been used for storage. A typical great house would contain a few of these suites, with a kiva for every two or three. It’s unclear what the relationships among different kiva-units within a great house would have been, but they could have either been separate extended families within the same real or fictitious “clan” or “lineage,” or they could have been separate lineages that were politically or ceremonially allied. Importantly, all of these buildings are still residential at this point, although the residents may well host rituals or feasts open to the whole community either to solidify their political authority or because generosity is expected of them in exchange for community acceptance of their greater wealth or political/religious authority. The main difference between great houses and small houses is just that great houses are bigger, with multiple stories in some instances and generally bigger rooms, as well as more extensive use of masonry rather than adobe or jacal construction.
Then, at some point in the 900s, a change takes place in some (all?) great houses. Use of the kivas is discontinued, and instead the activities that had been conducted in them are transferred to square surface rooms added onto the existing roomblocks. This definitely seems to be what happens at Una Vida and Peñasco Blanco, although the extent to which there were earlier kivas is unclear given the lack of excavation. In great houses newly begun during this time (it’s unclear how many of these there were in Chaco itself, but Kin Nahasbas may be an example), room suites were built without any kivas but with large, square rooms in front and smaller rectangular rooms varying in number behind them for storage. This pattern continues well into the 1000s, at least at some great houses, and it’s associated with the very formal, symmetrical, rectilinear layout seen at sites such as Hungo Pavi, Chetro Ketl, and Pueblo Alto. Some outlying great houses, such as Kin Bineola and (especially) Salmon, show this pattern as well. Salmon seems to show that new great houses with (almost?) exclusively square rather than round living rooms were still being built as late as 1090, and if the early construction at Aztec is in the same pattern, which seems to be a matter of some dispute, it would still be going on well into the early 1100s. This is probably also what we see at Pueblo Bonito too, with the possible addition of square rooms like 329 and 330 to the older suites at the west end of Old Bonito and the later addition of linear suites to the south of these rooms at the southwest corner of the site.
At some point in the late 1000s, however, a different type of room suite begins to arise at some Chaco great houses. This is still a linear suite, sort of, but it consists of a round kiva built aboveground into a first-story square room, with one or two rows of two- or three-story rectangular rooms extending back from it. These are the “blocked-in” kivas that are probably the most famous innovation of Chacoan architecture. I see them as still residential spaces, in combination with the rooms behind them. Their appearance at most outlying great houses indicates residential use of those sites, perhaps by local elites. It’s not clear what the relationship is between these plaza-facing blocked-in kiva suites and the “elevated” kivas surrounded by rectangular rooms that start to appear at the centers of the rectilinear great houses with the square living rooms around this same time. If those rooms are still residential, they’re pretty damn fancy residences. They’re also quite unlike the other residential rooms at these sites, which are still square. The “Tower Kiva” at Salmon is one example, as are the corresponding kiva at Hungo Pavi and the numerous examples at Chetro Ketl. The central placement and unusual elaboration of these structures has led many to assume that they were ceremonial rather than residential in function, but I’m not so sure. These sites do generally have great kivas, which pretty much everyone agrees were community-scale ceremonial/integrative structures, and they look quite different from elevated kivas (although it’s not clear to what extent the unique features of great kivas are due to structural requirements following from their size).
In any case, the best examples of the plaza-facing blocked-in kiva suites are at Pueblo Bonito in the southeast and southwest wings. These appear to have been built over earlier construction, so it’s not totally clear what was going on with these multiple, quite rapid changes in site layout during this period. Again, though, they’re also obvious at Una Vida and Peñasco Blanco, where some (but not all!) of the earlier square living rooms are replaced by blocked-in kivas. This also appears to have happened in the west wing of Chetro Ketl, but it’s unexcavated so it’s hard to say for sure. There definitely are two blocked-in kivas there, though, and they appear to have rooms behind them like at Pueblo Bonito.
Then, at some point toward the very end of the eleventh century or very early in the twelfth, a totally new type of room suite begins to appear at Chaco great houses. This is the famous “McElmo unit,” with a central blocked-in kiva surrounded on three or four sides by rectangular rooms, most of them significantly higher (three or four stories), creating a sort of “patio” over the kiva. These rarely have ground-floor exterior walls, and they are remarkably uniform and modular in form. The most famous of these structures are the freestanding ones, including New Alto, Casa Chiquita, and Kin Kletso (which comprises two adjacent units), but clearly analogous forms can be seen within certain great houses, including the north and south wings of Pueblo del Arroyo and the Kiva B complex at Pueblo Bonito. Similar units that are just outside of existing great houses can be seen at Chetro Ketl and Peñasco Blanco. The masonry of most of these is very different from that used at earlier great houses, being composed of blocky yellow sandstone rather than fine, hard, dark sandstone, and this has been used to argue that they represent influence from the north. The masonry may indeed reflect northern influence (though in a different way from what the original proposers of this idea thought), but the form predates the shift in masonry and probably developed locally in Chaco.
There has been a lot of debate over the function of McElmo units. Some see them as warehouses, while others see them as ritual (or possibly astronomical) special-use sites. I’m increasingly thinking that all this speculation is based on an overemphasis on their differences from earlier great houses, and that they were probably residential and represent the final version of the Chacoan room suite. More on this later.
McElmo units may represent the final development of Chacoan architecture in terms of form, but the great houses continued to be occupied for quite some time after the construction of these roomblocks in the early 1100s. What we see at this point is an increased emphasis on the blocked-in kiva concept, with new kivas, often of “non-Chacoan” form, being built into earlier square or rectangular rooms. Some call these “intra-mural” rather than “blocked-in” kivas, to emphasize that they were built into earlier rooms rather than having square rooms built around them, and I think this is a helpful distinction. These really proliferate at Pueblo Bonito late in the occupation period, and this also happens at Aztec and Salmon during their “post-Chacoan” (also called “secondary” or “Mesa Verdean”) occupations. At the same time, many great houses also see the construction of new subterranean kivas in the plazas, often with accompanying small blocks of square rooms. These aren’t usually datable directly, but they appear to be very late. Pueblo Bonito has particularly many of these, and there are a few in the southeast corner of Chetro Ketl too. These appear to represent the construction of typical small-house or unit-pueblo style residential units within earlier great houses, and they may or may not represent an occupational discontinuity of some sort.
So basically, what we see is a sequence of underground kiva to above-ground square room to above-ground kiva. There are plenty of variations and complications, but that’s the general sequence. The later use of intra-mural kivas, especially at Pueblo Bonito, has tended to obscure the middle stage here, but it really seems to represent something meaningful at least as a chronological marker in Chacoan architecture. Does it mean anything else culturally? That part I’m still looking into, but it may.