Center for Desert Archaeology

Dramatic changes occurred in the lower San Pedro Valley in the A.D. 1200s. By 1300, all of the valley's residents had moved from dispersed pithouse settlements into more concentrated masonry and adobe villages. The San Pedro flood plain was covered with maize fields fed by canal systems up to 5 miles long. Each canal system was built and maintained by an irrigation community containing between 100 and 300 people.

Beans and squash were also cultivated. Mesquite beans and various cacti fruits were favorite gathered resources. An occasional trip was made to obtain juniper berries from the mountain slopes far above the floodplain. Although cotton was grown in other river valleys of central and northern Arizona, we encountered no evidence of this raw material for textiles. Even more conspicuous is the near-absence of agave, considering the thousands of rock piles, presumably used in cultivating this plant, that line many of the terraces overlooking the floodplain. These agricultural features apparently fell out of use by the mid-1200s, as the later inhabitants focused their subsistence efforts on the floodplain near their villages. These areas were easy to monitor and protect from outsiders.

During the late 1200s, platform mounds were built in 11 of the irrigation community centers along the 35-mile stretch of the river from Dudleyville near the Gila River confluence to Redington. Although the social function of platform mounds is unclear, they would have been prominent territorial markers on the landscape for each irrigation community.

On a larger organizational level, platform-mound settlements and corresponding irrigation communities can be grouped into two districts based on location and differences in artifact assemblages. The Aravaipa District includes a cluster of four mound villages and associated settlements near the mouth of Aravaipa Creek. This district is one of the most fertile in the valley, and there is an extended history of settlement in the area. Artifacts from Aravaipa district settlements suggest limited interaction with outside groups and close links with the inhabitants of earlier pithouse settlements in the vicinity, particularly the Big Ditch ballcourt village near Ash Terrace. Some of the inhabitants of Big Ditch produced pottery that imitated buff wares manufactured in the middle Gila River Valley, indicating strong links with the Hohokam.

This tradition of pottery production was continued in the Aravaipa district during the Classic period (1200-1450), with one or more settlements making many of the San Carlos Red-on-brown and red ware vessels recovered from the lower valley. San Carlos Red-on-brown is the only Classic period decorated ware found in quantity that was produced by groups with deep historical roots in the region.

The San Manuel District was comprised of six mound villages and associated settlements dispersed along a 22-mile stretch of the river from Leaverton Mesa to Second Canyon, the southern-most platform mound in the valley. Except for Leaverton Mesa, the regular 4- to 5-mile spacing of mounds roughly coincides with inferred canal networks, suggesting one mound for each irrigation community. Beginning in the early 1300s, and continuing throughout much of the century, platform-mound settlements in this district were abandoned in a gradual retraction of settlement toward Aravaipa Creek and the Gila River. Platform mounds suggest strong Hohokam connections, and the ample quantities of San Carlos Red-on-brown and red wares indicate contact with Aravaipa-district settlements. However, the San Manuel-district residents were also interacting closely with various migrant groups who were arriving in the lower valley during the Classic period.

This interaction is best demonstrated by the distribution of locally produced corrugated pottery. Corrugation is a tradition associated with Ancestral Pueblo groups to the north and east of the valley. In the San Pedro Valley, corrugated pottery had a brief history, largely confined to the late 1100s and early 1200s. Within this narrow time frame, the density of corrugated wares is remarkably uneven, peaking in the heart of the San Manuel district and rapidly dropping off in the outer mound villages. Hence, a number of corrugated pottery-producing households entered the lower San Pedro valley at the beginning of the Classic period, possibly from the Safford Basin, Point of Pines, or areas farther north. Many of these households settled within or near local settlements in the San Manuel district. Other groups moved into favorable bajada settings north of Big Bell, and several even traversed Redington Pass to enter the northeast Tucson Basin. Very few producers of corrugated pottery settled in the Aravaipa district.

This earlier population influx paved the way for long-distance migrations that began in the late 1200s, which is roughly contemporaneous with the construction of platform mounds and adobe compounds. This second migration continued into the 1300s, and included families who originated in the Kayenta and Tusayan regions of northeastern Arizona, some 300 miles to the north. They traveled along a well-established migration route that extended south from the Four Corners area through Point of Pines, the Safford Basin, and ultimately into the lower San Pedro Valley.

Two San Pedro migrant enclaves, Reeve Ruin and the Davis Ranch site, excavated by the Amerind Foundation in the 1950s, are located 8 miles south of Second Canyon, the southernmost platform mound in the San Manuel District. Other potential enclaves in the Cascabel District were identified by the Center. These sites extend nearly to the southern end of the lower San Pedro Valley. Kayenta/Tusayan settlements can be distinguished from local and other migrant settlements by the presence of perforated plates, Maverick Mountain series pottery, kivas, and unique elements of domestic architecture that have their origins in northeast Arizona.

In addition to the architectural transformations discussed above, the arrival of long-distance migrants coincided with several dramatic changes in artifact assemblages. The frequency of obsidian, ideal for making razor-sharp projectile points, increased dramatically by 1300. Most of this material derived from sources in or near the Safford Basin along the migration route from the north. The Kayenta/Tusayan migrants appear to have had much greater access to obsidian than local groups and may have controlled obsidian distribution within the valley. Live macaws from Central America may also have been entering the valley with migrant groups and traded to local settlers. Finally, decorated ceramics increased dramatically in lower San Pedro assemblages at this time, including Maverick Mountain series pottery and Roosevelt Red Ware (Salado polychromes), which are linked stylistically and technologically with the Kayenta/Tusayan migrants. During the first half of the 1300s, Gila Polychrome, the most prevalent Roosevelt Red Ware type, appeared and eventually dominated decorated ceramic assemblages throughout the lower valley.

Our initial hypothesis--that long distance migrants were producing most of the Roosevelt Red Ware vessels, both for their own use and trade with the local inhabitants--was confirmed by petrographic analysis of sand used as ceramic temper material. Migrant settlements in the Cascabel district were the principal producers of Roosevelt Red Ware until the sites were abandoned in the late 1300s. Both obsidian and Roosevelt Red Ware vessels were exchanged by Kayenta/Tusayan migrants with local groups in substantial quantities. One wonders what the migrants were getting in return--perhaps maize and other irrigated crops grown by the locals.

Despite this harmonious picture of trade and co-residence between various migrants and local groups, the location of several settlements suggests social tension and perhaps even overt conflict. High Mesa and Leaverton Mesa, in the San Manuel district, are in walled defensible locations. These two settlements anchor the district flanks on the eastern side of the river, protecting the less-defensible central mound settlements from both the migrants in the Cascabel district and local groups in the Aravaipa district. The Reeve Ruin enclave is in a similar walled defensible position. These fortified settlements suggest that the various groups were at least suspicious of each other, if not openly hostile at times. However, the indefensible locations of the Davis Ranch migrant enclave, immediately across the river from Reeve Ruin, and the Second Canyon platform mound, presumably occupied by local groups, suggest that there was little conflict. It is likely that migrant and local populations engaged in both cooperative and competitive social relations during the century or so they both inhabited the valley.

Many sites in the northern Dudleyville District are associated with large quantities of Tonto and Cliff polychromes, the latest of the Roosevelt Red Ware types. During the late 1300s and early 1400s, settlement in the valley was concentrated in this district. Many of the settlements south of Aravaipa Creek were abandoned by this time. A sherd of Rio Grande Glaze Ware C recovered from Flieger Ruin in the Aravaipa district indicates that this settlement may have endured past 1425, slightly more than a century before the arrival of the Spaniards. Limited evidence and analogies drawn from comparable late settlements in southeastern Arizona, southwestern New Mexico, and in the Phoenix Basin suggest that these late sites were occupied by groups who were descended from both local and migrant populations.

After several generations of close interaction and intermarriage, an entirely new social identity may have emerged, with connections to both the developing Puebloan World and the declining Hohokam world. The inhabitants of these sites also made Roosevelt Red Ware vessels and had access to obsidian from a distant source near Flagstaff, attesting to continued ties with northern Arizona. As the population declined, the inhabitants of these final settlements may have increased their contacts with the occupants of adjacent river valleys for trade and marriage partners.

By 1450, even the last Classic period occupations in the north were terminated. No archaeological sites have been found that date to the next 200 years, suggesting that very few people were living in the valley until the arrival of the Sobaipuri, the inhabitants of the region when the Spaniards first settled in southern Arizona in the late 1600s. Sobaipuri sites and artifacts are dramatically different from those associated with the Classic period inhabitants, and it is difficult to infer that the two populations are related. Understanding how such a lush region could have been unoccupied for so long requires us to look outside the San Pedro Valley to adjacent valleys of the southern Southwest and beyond. Stay tuned...

(This article was excerpted from Archaeology Southwest volume 17, number 3. Members can view the complete issue on-line in the Members-Only section of this website. Nonmembers can purchase a copy in the Bookstore section.)