Several decades ago, the National Park Service's Chaco Project revealed evidence for widespread ornament manufacture at small sites (small houses) in Chaco Canyon, New Mexico, as well as possible workshop-scale production at two of these locations. Given that consumption of finished jewelry items is clearly concentrated at large sites (great houses), it was suggested that lapidary production was part of a larger corporate political strategy, in which goods produced in surrounding small houses were used to sustain communal events related to construction activities and ritual performances at great houses. This article addresses a critical gap in this narrative—ornament production at great houses. Using Pueblo Bonito as a case study, I present the results of a systematic analysis of lapidary tools from the site and characterize the nature of on-site ornament manufacture. I find evidence that significant jewelry-making was occurring at Pueblo Bonito, at least on par with previously documented small-house jewelry workshops, and that a portion of this was embedded within elite households. These results require us to reconsider the role of ornament production in Chacoan political economy.

Monumental roads were constructed during the ninth to thirteenth centuries by the regional society centred on Chaco Canyon in the US Southwest. Here, the authors present new lidar and field documentation of parallel roads at the Gasco Site, which sits within a ritual landscape south of Chaco Canyon. Their findings reveal that the Gasco Road is substantially longer than previously believed and forms alignments between natural springs and towards the winter solstice sunrise over Mount Taylor, a mountain sacred among contemporary Indigenous peoples. These findings highlight the agency of landscapes and skyscapes in structuring ritual practices in ancient societies worldwide.

Humans inhabit rich social and physical worlds and archaeology is increasingly engaging with the multi-sensory experience of life in the past. In this article, the authors model the soundscapes of five Chacoan communities on the Colorado Plateau, where habitation sites cluster around monumental great houses. The work demonstrates that the audible range of a conch-shell trumpet blown from atop these great houses consistently maps the distribution of associated habitation sites. Staying within the audible reach of great houses may have helped maintain the social cohesion of communities in the past which, the authors argue, also has implications for the management of archaeological landscapes in the modern world.

Despite considerable developments in the archaeological application of lidar for detecting roads, less attention has been given to studying road morphology using lidar. As a result, archaeologists are well equipped to locate but not thoroughly study roads via lidar data. Here, a method that visualizes and statistically compares road profiles using elevation values extracted from lidar-derived digital elevation models is presented and illustrated through a case study on Chaco roads, located in the US Southwest. This method is used to establish the common form of ground-truthed Chaco roads and to measure how frequently this form is across non-ground-truthed roads. This method is an addition to the growing suite of tools for documenting and comparing roads using remotely sensed data, and it can be particularly useful in threatened landscapes where ground truthing is becoming less possible.

The construction of great houses during the Bonito Phase (ca. AD 850–1200) in Chaco Canyon, New Mexico, required massive amounts of building material and efficient mobilization and coordination of large labor pools. We employ least cost path analysis (LCA) to explore the potential communication network among great house communities in the Chaco “core” area and its relevance in managing sustained labor for constructing great houses. The results suggest that that the primary sources of labor for communal building projects were agricultural communities located within one to three hours of the largest buildings in the canyon.

We report here the first domesticated amaranth (Amaranthus spp.) seeds to be identified at a Chacoan great house, from the northern New Mexico site known as Aztec North, where they were found in a context that dates to the mid to late twelfth century AD. Amaranth has long been recognized as an important prehispanic resource in this region, evidenced by the archaeological record of both wild and domesticated forms and by the traditional knowledge and practices of Indigenous communities. Wild amaranth and similar-appearing chenopod/goosefoot (Chenopodium spp.) seeds are routinely found in Ancestral Puebloan contexts. Recent archaeological testing at the Aztec North great house, a Chaco Canyon outlier associated with a post-Chacoan political center, has revealed the presence of uncharred domesticated amaranth seeds in a thin layer of ashy trash in a room at the rear of the great house. These seeds expand our understanding of domesticated amaranth in the American Southwest and suggest centuries of continuity of traditional amaranth cultivation within Puebloan communities.

The iconic Plaza Tree of Pueblo Bonito is widely believed to have been a majestic pine standing in the west courtyard of the monumental great house during the peak of the Chaco Phenomenon (AD 850–1140). The ponderosa pine (Pinus ponderosa) log was discovered in 1924, and since then, it has been included in “birth” and “life” narratives of Pueblo Bonito, although these ideas have not been rigorously tested. We evaluate three potential growth origins of the tree (JPB-99): Pueblo Bonito, Chaco Canyon, or a distant mountain range. Based on converging lines of evidence—documentary records, strontium isotopes (87Sr/86Sr), and tree-ring provenance testing—we present a new origin for the Plaza Tree. It did not grow in Pueblo Bonito or even nearby in Chaco Canyon. Rather, JPB-99 originated from the Chuska Mountains, over 50 km west of Chaco Canyon. The tree was likely carried to Pueblo Bonito sometime between AD 1100 and 1130, although why it was left in the west courtyard, what it meant, and how it might have been used remain mysteries. The origin of the Plaza Tree of Pueblo Bonito underscores deep cultural and material ties between the Chaco Canyon great houses and the Chuska landscape.

Recent geophysical remote sensing, including ground-penetrating radar and magnetometry, has been used to investigate three areas within Chaco Canyon, New Mexico, predicted to contain prehispanic agricultural fields. These localities include a well-known but enigmatic area of large grid patterns near the Chetro Ketl great house, which are visible from the air but not at ground level. The gridded area has been interpreted by many researchers as an agricultural field system, and this perspective has in turn been utilized to model agricultural land use throughout the canyon, particularly intensification associated with emergent social complexity. The geophysical surveys revealed evidence of buried features at all three study areas, but the patterns expressed by these features do not clearly conform to the pattern predicted in the gridded agricultural field model. We argue that the surficial grid pattern seen at the Chetro Ketl field is an unusual example of land modification in the canyon and thus unlikely to represent typical Chacoan agricultural field systems. Instead, canyon residents employed a diverse range of agricultural techniques suited to the variable and patchy nature of canyon hydrology and soils.

Migration was a key social process contributing to the creation of the ‘Chaco World’ between AD 800 and 1200. Dynamic social network analysis allows for evaluation of several migration scenarios, and demonstrates that Chaco’s earliest ninth-century networks show interaction with areas to the west and south, rather than migration to the Canyon from the Northern San Juan. By the late eleventh century, Chaco Canyon was tied strongly to the Middle and Northern San Juan, while a twelfth-century retraction of networks separated the Northern and Southern San Juan areas prior to regional depopulation. Understanding Chaco migration is important for comprehending both its uniqueness in U.S. Southwest archaeology and for comparison with other case studies worldwide.

Pueblo Bonito in Chaco Canyon is one of the most iconic pre-Hispanic archaeological sites in the U.S. Southwest. Archaeologists refer to it as a great house in recognition of its massive scale, and often describe it as the centre of the Chaco world. Yet questions remain about Pueblo Bonito’s origins, sequence of construction, duration of occupation and abandonment. Here, the authors present new research that helps to clarify the early phases of occupation, and illuminates some of the problems inherent in reconstructing a building that was a perennial work in progress.

The Pueblo population of Chaco Canyon during the Bonito Phase (AD 800–1130) employed agricultural strategies and water-management systems to enhance food cultivation in this unpredictable environment. Scepticism concerning the timing and effectiveness of this system, however, remains common. Using optically stimulated luminescence dating of sediments and LiDAR imaging, the authors located Bonito Phase canal features at the far west end of the canyon. Additional ED-XRF and strontium isotope (87Sr/86Sr) analyses confirm the diversion of waters from multiple sources during Chaco’s occupation. The extent of this water-management system raises new questions about social organisation and the role of ritual in facilitating responses to environmental unpredictability.

Three architectural traditions with astronomical associations have been identified among the ‘Great Houses’ and ‘Great Kivas’ of Chaco Canyon, New Mexico. Great Houses and one Great Kiva built during the height of construction activity (AD 1020–1100), the Bonito Phase, include front-facing south-southeast (SSE) orientations, and cardinal north-south and/or east-west (NS/EW) alignments. We present ethnographic material supporting our previous proposal that the SSE orientation is probably linked to migration traditions and ancestor veneration. We also confirm that a majority of Late Bonito Phase Great Houses (built after A.D. 1100) exhibit a third astronomical tradition: five of the principal in-canyon Great Houses built at that time were positioned at or near observing locations that could have functioned as solstice calendrical stations. Through use of these locations for public ceremonies, the Chacoan elite could demonstrate astronomical knowledge and ritual power. These findings provide support for Van Dyke's hypothesis that construction during this period was intended to reinvigorate a faltering system. One ‘Chaco halo’ Great House, Bis sa'ani, incorporates all three traditions. We suggest that temporal analysis of these traditions improves understanding of migration paths and shifting balances of power and social dominance among ancestral Pueblo culture groups.

During its development years, geophysical survey has served field archaeology by defining possible sites underground, prior to excavation or preservation. Now we can see the art taking off as a research method in its own right. After summarising some recent research applications of magnetic mapping, the author gives us three case studies from USA and Jordan, where ground-penetrating radar (GPR) has produced new interpretations of prehistory and history. Since GPR can map in horizontal slices without damage, it opens up important heritage preservation options. In one case, excavation was discouraged on ethical grounds, in another it was inhibited by the presence of later monuments and in a third, an early agricultural site, the GPR actually saw more than the excavators. This presages a research tool of particular power.

One of the strengths of the archaeological discipline is our ability to examine social transformations over the course of centuries or millennia. However, we rarely think about the ways in which temporal scale affects our interpretations of these processes. Transformative social changes look different when seen from the perspective of the longue durée, a human lifespan, or a single day. Although they clearly result from human actions, long-term, major social changes cannot be understood simply as additive concatenations of short-term shifts.