Bi-Walls and Tri-Walls

Only five of these structures have been excavated. The first is the tri-wall central, round area (room?) at the Hubbard Site (figure 17.1) at Aztec Ruins National Monument. It was originally constructed as a 7.2 m diameter structure, plastered, featureless, and possibly roofless. Subsequently (perhaps immediately), a shallow, 5.5 m in diameter, free-standing “kiva” (with hearth, deflector, etc.) was inserted into the space (Vivian 1959, 18). The interior walls of Hubbard tri-wall stand over 2 m tall, and the excavator estimated an original height of over 3 m (Vivian 1959, 16).

The second is the Pueblo del Arroyo tri-wall at Chaco Canyon (which the excavator, when referring to the central area of the structure, called a “McElmo Tower”) (Judd 1959, 109; see also Vivian 1959, 61–70). This structure was originally 6.4 m in diameter at ground level, fully or partially paved with flagstone, and largely dismantled. No interior features survived.

The Red Willow bi-wall, near Tohatchi, New Mexico, was excavated during a highway salvage project in the1960s (Peckham 1963). It’s located a short distance northwest of a small great house (the bi-wall and great house were recorded as a single site, LA 4470). The central round room, about 7 m in diameter at grade, has floor features associated with “kivas” (i.e., hearth, deflector, etc.) but lacked a “bench” and a floor vault. The excavator estimated the structure stood one story tall (Peckham 1963, 58).

The “Great Tower” at Yellow Jacket Pueblo (figure 17.3, near the town of that name in southwestern Colorado), the fourth structure, was reexcavated by Crow Canyon (Kuckelman 2003, 30–43). A trench revealed a floor with “kiva” features (a “bench,” low masonry pilasters, a central, round firebox, and a floor vault) in a 5.5 m diameter structure—a suite of features suggesting an elevated “Chaco-style kiva” (Lekson 1986, 54–59) (for reasons mysterious to me, now referred to as a “court kiva” [Windes 2014]). Unlike Hubbard, the interior wall of the concentric circle of rooms forms the wall of the kiva (Kuckelman 2003, 41); it seems likely that the kiva was an integral part of the larger bi-wall, although it could have been constructed inside the structure at a later date. The enveloping “tower” was originally two stories tall (Kuckelman 2003, 30).

Finally, a fifth “tri-wall kiva” was partially excavated at the Mitchell Springs Ruin Group, near Cortez, Colorado. It is interpreted as a Chaco-era “tower” standing over 3 m tall and enclosing a 4 m plus diameter Chaco-style kiva (with bench, hearth, and floor vault). The “tower” is surrounded by two rings of rooms attached to a great house (Dove 2021). The excavator believed that the central tower was three stories tall, surrounded by an inner ring of two-story rooms, and finally surrounded by an outermost ring of one-story rooms (Dove 2021, fig. 6). This is similar in configuration to the Holmes “tower” bi-wall above the San Juan River (figure 17.4) seen and illustrated by William H. Holmes (1876, pl. 3). The interior of Holmes’s bi-wall was about 3 m in diameter. “The wall is . . . from 2 to 6 feet in height. Long lines of debris, radiating from all sites, indicate that is has been much higher, and has but recently fallen” (Holmes 1876, 9). Holmes’s image—an artist’s reconstruction—shows a central, two-story tower, encircled by a ring of one-story rooms.

Bi-Walls and Tri-Walls as Kivas

Although the number of excavated bi- and tri-walls is small, preserved architecture is centered on “kivas” or “kiva-like” features, including hearths and deflectors, and in some cases benches, and vaults. If our small sample is, in fact, representative, we can infer that the central, round rooms in all bi- and tri-walls are so-called kivas. The appellation kiva does not mean they were principally ceremonial, ritual, or religious structures; it indicates primarily residential functions.

For those new to this argument, the term kiva, applied to round rooms in Chaco and Aztec, is an unfortunate misnomer (Lekson 1986, 50–51, 1988). In archaeological terms, kiva refers to a round room with a constellation of architectural features and should not of itself suggest ceremony. “For the last three decades archaeologists in the central Mesa Verde region have identified small kivas (with diameters less than 10 m) as serving a domestic function in addition to focusing some ritual activities at the level of the household, extended household, or lineage group” (Crabtree et al. 2017, 77). That is, small “kivas,” like those found in bi- and tri-walls, can be reasonably assumed to indicate residential, rather than purely ceremonial, functions, although household-level rituals and ceremonies undoubtedly took place.

The rooms encircling bi- and tri-walls are small and almost uniformly featureless. The Hubbard Site is the only tri-wall with walls sufficiently tall to reveal doors. At Hubbard, only the exterior row (of the two encircling rows) had doors. That is, the interior row lacked doors, and there is enough preservation in the architecture that doors would have been preserved and detected. Only one door (15A) opened to the exterior; it was large (“3 feet wide”) and there is no information on its shape, so I assume it was rectangular (from photos, it appears that this door was not preserved sufficiently to ascertain if it was T-shaped). All other doors opened between rooms in a circular, rather than radial, pattern; that is, the doors connected rooms in their tiers or concentric rows and did not open into the center or out to the exterior. These “doors are rather small, 1.7 to 2.3 feet wide and, where intact, 4 feet high with raised sills up to 1 foot above the floor level” (Vivian 1959, 17), almost certainly storage room doors (Lekson 1986, 25–28). In light of the small size of the encircling rooms recorded in all bi- and tri-wall structures, and consistent with storage rooms at great houses, I consider Hubbard’s doors indicative. The encircling rooms were probably designed for storage.

Holmes’s bi-wall “tower” may have inspired Jonathan Reyman’s (1985), and perhaps David Dove’s (2021), suggestion that bi- and tri-walls were towers surrounded by “stepped” rings of rooms, not unlike a tiered wedding cake. This interpretation has not garnered favor, but I find Holmes’s, Reyman’s, and Dove’s suggestions interesting and, along with Hubbard’s 3 m tall walls and Yellow Jacket’s two-story “Great Tower,” suggestive. The central, round space of at least some bi-walls and tri-walls may have been round towers. Round towers were numerous across the Four Corners at the same time (Bredthauer 2010; Glowacki 2015, fig. 23). Free-standing towers, however, generally lack floor features beyond the occasional fire pit (Bredthauer 2010), and to my knowledge none had “kiva” features.

To summarize, bi- and tri-walls were free-standing buildings, at least initially, centered on large Chaco-style “kivas,” surrounded by concentric rings of storage rooms. Some, but not all, were towers; and some tower bi- and tri-walls may have been tiered. My summary extrapolates from limited information, but that’s all the information we have.

Dating Bi-Walls and Tri-Walls

I’m not aware of any tree-ring dates unambiguously associated with bi- or tri-walls. A date of AD 1109c, once associated with the Pueblo del Arroyo tri-wall, comes instead from late construction activities attached to the main building (inserted between the main building and the free-standing tri-wall) (Lekson 1986, 223; corrected by Windes 2010). A date of AD 1148++vv from Hubbard is of uncertain provenience and may not be from Hubbard at all (Lekson 1983, 16). A date of AD 1254+vv from the “disturbed” fill of the central space in the Yellow Jacket “Great Tower” almost certainly comes from the complex of rooms (Square Mug House) built after the construction of the tower; early excavations redeposited fill from cleared rooms in Square Mug House into previously excavated units (Kuckelman 2003).

The ceramic assemblages at all five sites suggest occupations in the early AD 1100s through the mid-to-late AD 1200s—that is, contemporary with Aztec Ruins. All feature McElmo and Mesa Verde Black-on-white ceramic types; intriguingly, including the Red Willow bi-wall, 125 km south of Aztec Ruins and 150 km south of Mesa Verde proper.

Bi-Wall and Tri-Wall Function

Encircled by rings of rooms, bi-walls and tri-walls are riddles wrapped in mysteries inside enigmas. What are they? Kristin Kuckelman (2003, 43) notes: “Various uses have been suggested for multiwall structures, which are ‘ostentatiously different from ordinary residential structures in architectural form and setting.’ ” Researchers have theorized that these structures were used as residences for a developing priestly class; as intercommunity ceremonial centers; as fortresses, council chambers, and places of worship; or as platform mounds. William Lipe and Scott Ortman (2000, 111) suggest that some multiwall structures could have been residences “for one or two households that had access to significantly more than the usual amount of storage space, and perhaps had stewardship of important rituals.”

Lipe and Ortman (2000) recognized that small “kivas” dating to the tenth through thirteenth centuries AD were, as noted, primarily residences. Thus, the central “kiva” features of bi- and tri-walls marked residential rather than ceremonial functions. This is not to deny the presence and importance of ceremony but, rather, to emphasize that bi- and tri-walls were first and foremost residences, possibly of the “developing priestly class”—or another elite social stratum?

Kuckelman (2003, 43) concluded, “The unique design of these structures strongly suggests that they held special, possibly integrative, significance and were used for special activities that were important, exclusive, and restricted.” Glowacki (2015, 72–81) groups “multiwalled structures” together with great houses as “restricted-use architecture”—correctly, I think. Both were “oriented towards small-scale interactions among people who were members of a specific group (e.g., household, lineage, or non-kin ritual group)” (72–81). I suggest those “specific groups” were elites or, more accurately, nobles—hereditary elite classes commonly part of Native North American agricultural societies (discussed in Lekson 2018, 76–83). (Note that Glowacki also included D-shaped “multiwalled structures”; these interesting buildings have no counterparts at Chaco or Aztec—unless the “D” mimics the ground plan of Pueblo Bonito? Glowacki demonstrates that their geographic distribution differs from that of bi- and tri-walls, with D-shaped buildings occurring further west.)

Whatever their function(s), I suggested two decades ago that these buildings were architectural icons of Aztec Ruins and its regional system (Lekson 1999, 103). Aztec Ruins, in the twelfth to thirteenth centuries AD, was the successor capital (sensu Rapoport 1993) after Chaco Canyon in the eleventh and early twelfth centuries AD (Lekson 1999, 2015). This historical interpretation was initially controversial but today seems to be generally accepted (e.g., Reed 2008, 2011).

The Aztec Regional System

Aztec Ruins was centered on free-standing tri- and quadri-walls. Like Chaco, Aztec Ruins was a planned city with multiple great houses and other features built on sites determined by a larger design (Stein 1987, fig. 4; Stein and McKenna 1988, fig. 10; republished in Lekson 1999, fig. 3.6). For more recent invaluable work on the eastern half of the landscape, see Paul Reed et al. (2010). A largely unexcavated quadri-wall (Mound F) forms the center or focus of the plan. (Note that Reed et al. 2010 interpret Mound F as a large tri-wall structure, but my observations suggest three rows of rooms in four concentric walls; only the spade will tell.) Free-standing tri-walls, northeast and northwest of the quadri-wall, create points on two axes crossing through the central quadri-wall, aligning to the great kivas of Aztec’s two largest great houses: Aztec East and Aztec West. One of these tri-walls, the Hubbard Site, was excavated; the other, Mound A, remains unexcavated. Two additional small bi-walls (Mounds B and C) appear to be attached or associated with great houses in the Aztec East complex. That’s five bi-, tri-, and quadri-walled circular structures at Aztec Ruins, four more than any other site. Glowacki (2015, 76), in her excellent review of multiwalled structures, concluded, “The tri-wall form is decidedly linked to Aztec and its ritual and political organization.”

Archaeologists working in the San Juan area generally recognize Aztec Ruins as a second (smaller) Chaco but often downplay or discount its importance to the larger central Mesa Verde region. This omission is understandable, because we heretofore lacked evidence to delineate Aztec’s regional reach, much less to evaluate its dynamics. Chaco announced itself with great houses; many of those great houses continued through Aztec’s era but with significant changes in how they were used. Were they “hallmarks” of Aztec or relics of Chaco? ¿Quién sabe?

Bi- and tri-walls, I think, provide monuments on the landscape that can be reasonably linked to Aztec and only Aztec; they are one solid line of evidence to define Aztec’s region. Not big data, but a small set of clunkier evidence—forty-odd multiwalled structures. Bi- and tri-walled structures in the central Mesa Verde region have been documented and analyzed by Glowacki (2015, 72–81). She noted several multiwalled structures at southern sites but concluded “multiwalled structures were a decidedly northern San Juan phenomenon” (Glowacki 2015, 75). I am particularly interested in bi- and tri-walled structures far to the south of Aztec Ruins, including structures near Tohatchi, New Mexico; Manuelito, New Mexico; and Ganado, Arizona—as far as 200 km from Aztec. In contrast, in the Mesa Verde region proper, the most distant bi-wall (near Aneth, Utah) is about 115 km from Aztec. (In my opinion, there is a high probability of more, undiscovered bi- and tri-wall structures in the north and especially in the south; the intensity of research in the northern San Juan dwarfs the work done south of Chaco, on the Navajo Nation, and Zuni Pueblo.) If, as I argue, bi- and tri-walls mark Aztec’s regional extent in the north, what about those southern sites?

Clunky evidence, at last, meets big data. The Southwest Social Networks Project is an outstanding big data initiative led by Barbara Mills, Matt Peeples, and others. This remarkable project recently analyzed social networks based on ceramics in fifty-year increments in the time of Chaco and Aztec (Mills et al. 2018). To summarize one aspect of their fruitful study, two densely interconnected social networks consistently appeared, one to the north of the San Juan River and a larger network to the south, centered on Chaco but extending well into Arizona to the Mogollon Rim (figure 17.5). During the AD 1100–1150 period—Aztec’s rise—a third network emerged:

Interestingly, during the AD 1100–1150 interval, our community-detection analyses show three communities: the large northern and southern communities divided along the same lines seen in earlier intervals, and a third component (in yellow) that represents sites along the edges of these two larger communities . . . Another interesting result is that the cluster of Chaco structures near Aztec is not as central to the network as might be expected, although Aztec itself is. Aztec’s ascendency as the capital of the Chaco World (e.g., Lekson 2015) is especially evident in the AD 1150–1200 interval during the “post-Chaco” period. (Mills et al. 2018, 933–936).

In figure 17.6, I impose a white polygon of the approximate distribution of bi- and tri-walled structures. Their distribution bridges northern and southern networks, including over two-thirds (but, significantly, not all—as Glowacki noted) of the northern and a much smaller proportion of the southern. And, intriguingly, the distribution of multiwalled structures encompass most of the emergent “third component.” The smaller set of clunky evidence complements big data, and vice versa! They show different geographies; if bi- and tri-walls define Aztec’s regional system, that system incorporated parts of both northern and southern networks, but only parts. This should not surprise us—ceramics define one set of social dynamics, and monumental architecture another. Ceramics—the big data of social network analysis—track daily interactions, craft economies, and less-frequent distant contacts, things that we today might call “social.” Chacoan monuments—the relatively small number of great houses, roads, tri-walls, and so on—track interelite communication, power projection, institutional infrastructure, things that we today would call “political.” (For those favoring ceramics over buildings, the “third network” provides an intriguing parallel patterning between the two.)

Aztec’s political structure overarched strongly regionalized social networks—a polity encompassing varied local economies, ethnicities, languages, and so forth—much like Chaco’s earlier region (see Lekson 2018, chap. 4). However, Aztec and its region were smaller and, ultimately, less successful.

Bi-walls and tri-walls, remarkably prominent at Aztec Ruins, were symbols of the new order, similar to, yet distant from, Chaco Canyon. The sole tri-wall at Chaco Canyon, at Pueblo del Arroyo, was either never completed or was razed prior to AD 1300; it played a role at Chaco but only a transitory role. With the shift of the capital north, Aztec developed new symbols of power based on traditional architectures; elements of the common “unit pueblo” transformed into habitations “ostentatiously different from ordinary residential structures” (Lipe and Ortman 2001, 111). It seems likely that bi- and tri-walls located in larger settlements marked the apartments of elites or nobles. But it didn’t last. With Aztec’s collapse and the depopulation of the Four Corners, many of the social/political system’s markers were scraped off (Lipe 2010). Architectural forms associated with Chaco and Aztec disappeared from the Pueblo region, while a few reappear far to the south in the Casas Grandes region, most notably, the T-shaped door (Lekson 1999, appendix A, 2021).

Sightings of “bi-walled structures of a different sort” in the late prehistoric and protohistoric Rio Grande (Peckham 1963, 70) stretch beyond the modulus of elasticity; the Rio Grande sites are not bi-walls as defined here. Charles Di Peso’s (1974, 208) claim for similarities between Aztec’s tri-walls and Cerro de Moctezuma (the walled signal tower high above Paquimé, the Casas Grandes capital) has not survived subsequent research and mapping (Pitezel 2007). Bi-walls and tri-walls, like Aztec and Chaco, were erased from Pueblo life, along with the social/political systems they represented.

Acknowledgments. My thanks to Winston Hurst for showing me the Aneth bi-wall, westernmost of its ilk. And to Matt Peeples for permission to use his fascinating maps of social networks (figures 17.5 and 17.6). And to Cathy Cameron for her careful reading and correction of this text. All errors, of fact or of fiction, are of course my own.

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