Archaeological Periods in the San Pedro River Valley
Main Source: Patrick Lyons, "Archaeology of the San Pedro River Valley", Archaeology Southwest Winter 2004, p. 3-4.
According to Lyons, the archaeological record of the San Pedro River Valley may be divided into the following series of Periods:
Paleoindian (11,000 B.C. to 8500 B.C.)
A cooler, wetter climate prevailed, with a now-extinct Pleistocene Megafauna hunted by small, mobile bands whose members followed the herds and gathered wild plant foods. Spear-throwers (the Atlatl) were used to bring down these large animals.
Archaic (8500 B.C to 1700 B.C.)
As the climate became warmer and drier, the Megafauna died off, and people hunted deer and small game, relying more on wild plant foods. Ground stone tools for crushing and grinding seeds and nuts, and roasting pits for cooking plant foods became common. People moved seasonally between the uplands and lowlands, following different wild food sources.
Early Agricultural (1700 B.C to A.D. 50)
As domestic crops appeared -- corn, beans, squash, cotton, tobacco et al -- people began constructing the first permanent year-round settlements, with formal cemeteries and, in some places irrigation canals. Plainware pottery appeared, and the bow and arrow may have replaced the spear-thrower.
Pre-Classic (A.D. 50 to 1200)
Groups became increasingly dependent on agriculture, build large villages and extensive irrigation networks, produced painted pottery and exchange of pottery and shell jewelry intensified. During this time, the archaeological complex of the Hohokam Culture (whose center of gravity developed further downstream in the Gila River Drainage) extended in an upstream direction along the San Pedro River Valley. The Hohokam show strong influence from Mesoamerican cultures: Platform mounds and ballcourts, characteristic features of Central American cultures at this time, appeared in the Gila drainage, and cremation of the dead. Since the Hohokam tradition is so central to the San Pedro River Valley, we provide this general overview of its archaeology here: A Hohokam Chronology. During the late Pre-Classic period, "immigrants from the Mogollon Highlands moved into the valley and began to make corrugated pottery." (Ibid. p. 3)
Classic (A.D. 1200-1450)
During the Classic period, these immigrants constructed walled villages with above-ground rooms, and the platform mounds seen in the lower Gila River basin appeared along the San Pedro River as well -- 11 villages with platform mounds are found here. By A.D. 1300, groups of Pueblo (Anasazi) people from Northern Arizona moved into parts of this valley, bringing distinctive Pueblo pottery and architectural features including a Kiva ritual structure. Many of the villages show evidence of fortification during this time.
By 1450, archaeological evidence suggests that the valley was depopulated. Sometime after 1450, the Sobaipuri and Apache were present in the the area, engaging in various kinds of relationships that culminated in the departure of the Sobaipuri (O'odham Pima-speakers) from the valley. Apache speakers were driven out by Anglo settlers in the 19th century (though their descendants continue to use the area today).