Desert Archaeology research on the Early Ceramic period

Time of Transition: The Early Ceramic Period in the Tucson Basin

Homer Thiel discusses the state of our knowledge—and lingering questions—about the Early Ceramic period.

Around AD 50, the lives of the Native Americans living in the Tucson Basin began to dramatically change. This was the start of what archaeologists call the Early Ceramic period (also known as the Agua Caliente phase), a time span that lasted until sometime between roughly AD 500 and 540. During this 500-year period, people in southern Arizona developed new architecture styles and storage technologies.

Early Ceramic Period Archaeology

The Early Ceramic period was poorly known prior to the early 1990s, when two archaeological projects related to road construction encountered  materials dating to this crucial five-century block of time. In the eastern Tucson Basin, Statistical Research, Inc., excavated portions of the Houghton Road site prior to the realignment of that road, and near the Santa Cruz River, Desert Archaeology conducted excavations at the Square Hearth and Stone Pipe sites prior to frontage road work along Interstate 10. Additional Early Ceramic sites explored since then in Tucson include the Mission Garden locus of the Clearwater Site near Sentinel Peak (A-Mountain), the Valencia Vieja site near Pima Community College’s Desert Vista campus, and the Paseo site near the Santa Cruz River, south of Silverlake Road.

Desert Archaeology Early Ceramic tucson prehistoric

An aerial photograph of the Paseo Site, showing archaeologists excavating several pit structures dating to the late portion of the Early Ceramic period (photo by Henry Wallace).


These projects have uncovered dozens of pit structures, thousands of artifacts, and the remnants of meals in the form of animal bones, charred plant remains, and plant pollen.


A previous blog post discussed Early Agricultural period (2100 BC-AD 50) architecture, which mostly consisted of small, round pit structures. During the Early Ceramic period there was extensive architectural experimentation. The early portion of the Early Ceramic period saw the creation of “bean” shaped houses with an entranceway in the center of the long wall (Figure 2).

Desert Archaeology Early Ceramic tucson prehistoric

Feature 44 was a bean-shaped pit structure at the Stone Pipe Site. It had adobe pillars at the entranceway.


Many of these were true pithouses, meaning the interior pit walls (sometimes plastered) formed the actual walls of the house,  with the posts that formed the upper portion of the walls set into the ground on the exterior of the pit. A covered entrance was located along the long axis of the house. House pits were often dug deep enough that a step was required to get down onto the main floor. Often a pair of adobe bolsters or cones is located right inside the entranceway, surrounding the posts that held up the wall at that spot.

Desert Archaeology Early Ceramic tucson prehistoric

Feature 57 was one of the earliest pit structures at the Paseo Site. It had adobe bolsters at the juncture between the house floor and the entranceway.


A few postholes might be present inside the house, showing the locations of the posts that helped to hold up the roof. At the Square Hearth Site, several houses were found with plastered square hearths (the small, shallow firepits used to heat the house), while other houses have the more typical round hearths. Houses were substantial enough that they were probably used for several years.

To date, this abrupt transition from the small round houses of the Early Agricultural period to the more substantial Early Ceramic period houses cannot be explained. No transitional houses with remnants of Early Agricultural architectural traits have been found. It is possible that new people with their own architectural traditions immigrated to the Tucson Basin from outside regions, or that people from Tucson observed houses like this elsewhere and copied the architecture in their own settlements, or that the people living in Tucson decided on their own to become more sedentary and invest more energy into house construction.

The later portion of the Early Ceramic period saw even more architectural experimentation. At first houses became almost square or rectangular, but with rounded corners, again with an entranceway projecting outward on one long side. These houses continued to be true pit structures.

Desert Archaeology Early Ceramic tucson prehistoric

Feature 392 at the Stone Pipe Site dates to late in the Early Ceramic Period. It had partially plastered walls, indicating it was a true pit structure, and eight postholes showing the locations of interior posts that helped to support its roof.


Finally, houses became more rectangular with squared off corners. At times, the shapes and sizes of the houses and the locations of entranceways varied dramatically, a trend that continued on into the Tortolita phase (AD 500-700) of the Hohokam Pioneer period.


Between growing seasons, Early Agricultural period people apparently stored their maize harvests in some sort of perishable containers (woven baskets and animal hide bags), placing them in bell-shaped pits that were located outside their pithouses or inside specially-built pit structures with large central pits. The Early Ceramic period folks largely abandoned in-ground storage pits and instead constructed large, round seed jars.

Desert Archaeology Early Ceramic tucson prehistoric

A broken seed jar found on the floor of Feature 7, a pit structure at the Paseo site.


The jars are slightly flattened globes, with the top appearing to be sliced off.

Desert Archaeology Early Ceramic tucson prehistoric

Seed jar profiles from the Clearwater Site and a reconstructed seed jar from the Stone Pipe Site (drafted by Robert Ciaccio).


Ceramic disks, fashioned from large pottery sherds, are sometimes found. The diameter of the disks match jar openings, and it is likely that they were affixed with mud onto the opening to seal the jar shut. This prevented moisture, insects, and rodents from getting into the jar and spoiling its contents.

Desert Archaeology Early Ceramic tucson prehistoric

Worked sherd disks that served as tight-fitting lids with their matching seed jar rims from the Clearwater site.


Most of the ceramic vessels we find in the oldest Early Ceramic period houses are seed jars, with few other vessel forms present. Gradually, additional jar shapes were added to the ceramic repertoire, including some with short raised rims, along with bowls.

As noted above, very few storage pits are found at Early Ceramic period sites, although we sometimes find small storage houses that lack formal entranceways and hearths. Feature 4419 at the Mission Garden locus of the Clearwater Site had five broken jars on its floor.

Desert Archaeology Early Ceramic tucson prehistoric

A view of Feature 4419, a storage structure with five seed jars on its floor at the Mission Garden locus of the Clearwater site.


Five storage houses were found at the Paseo site, scattered among the 17 late Early Ceramic period dwellings present. The use of separate storage buildings again suggests more permanent residency in the settlements, along with a desire to keep the bulky jars away from the living space of the main dwelling.

What was stored in the jars? Maize has been grown in the Tucson Basin for at least 4,000 years. Farmers may have raised beans beginning at the end of the Early Agricultural period. Pumpkins were definitely grown during the Early Ceramic period, but it is uncertain whether they would have been stored in vessels. During the historic period, pumpkins and squash were cut into strips and hung on string to dry. Besides these domesticates, people were also harvesting weedy plants growing in their fields and gathering cactus fruit and mesquite pods. Animal bones recovered reveal that the farmers ate the cottontails and jackrabbits that invaded their fields, and occasionally hunted deer, either along the Santa Cruz River or in the nearby mountains.

Future Archaeology

A relatively small number of Early Ceramic period sites have been explored. Each excavation provides new data that help us better understand what life was like during this time. We have many questions, especially regarding the origins of the seed jars that appeared during the early years of the Early Ceramic period. Did someone bring pottery making technology to the region or did it develop here? Did the architectural changes that we observe occur throughout the region, or did it only take place in the Tucson Basin? Was there contact with the contemporary Red Mountain phase people in the Phoenix Basin? These and other questions can only be answered by archaeologists continuing to explore Early Ceramic sites.

Fieldwork for the projects discussed in the text was funded by Pima County, the Arizona Department of Transportation, and the City of Tucson.


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