Timeline for the People of the Four Corners Area - The Pecos Classification

In 1927 a group of archaeologists specializing in southwestern prehistory gathered to discus their season's work. It was here that the "Pecos Classification" system of dividing Anasazi (Ancient or Ancestral Puebloan) cultural development into different stages took shape. Originally intended to describe the eight identified stages of Southwestern prehistory; they did not apply dates to the stages.

Two years after the first Pecos conference the science of tree-ring dating was applied to sites in the region providing exact dates for several structures. By comparing different construction types, pottery types, and other stylistic attributes with exact dates given by the tree-ring dating method, archaeologists determined that different changes in pottery styles, architectural styles, etc. occurred at different stages.

The dates applied to each stage didn't necessarily apply to the entire region at once, and in the decades since that original gathering of archaeologists, the phases have been modified to account for variations within different regions. Different groups within the same region adopted different changes at different times. Because of this the dates that are given for each period are general at best.

Below are outlined, in general terms, the first six periods or phases of Anasazi cultural development, from the Archaic hunter-gatherer period, to the Pueblo III (PIII) that saw the depopulation of the Four Corners area at the end of the 13th century, according to the Pecos Classification.

Archaic: c.7000 - c.100 B.C. (formerly referred to as Basketmaker I)

The Anasazi are believed by archaeologists to have developed from the “Archaic” culture; groups of nomadic, hunter-gatherers, indigenous to the Four Corners area. During the later phases of the period, it covers a large time-span, people from the Archaic begin to rely less on hunting big game and more on collecting a variety plant foods. The domestication of planted crops begins during the late archaic and groundstone used in processing seeds during this period are abundant. They didn't leave much in the way of archaeological evidence, with the exception of abstract and representational rock art, isolated stone tool artifacts, and the remains of scattered campsites.

Basketmaker II: c.100 B.C. to A.D. 600

Named for their beautiful basketry and woven sandals, the early Basketmakers (BM) were still reliant on wild food sources, hunting with spears or atlatls (the bow and arrow had not yet been developed) but, were beginning to grow and store crop foods; maize (hard flint-corn) and squash, but no beans yet. They stored their food in deep covered pits or small slab-lined-cists. Often dwelling in caves or alcoves, they also built above ground, circular log houses or, in the later period, shallow pithouses. At this stage, they had not yet begun to make pottery.

Basketmaker III: c. A.D. 600 to 750

Three important changes set the BMIII apart: plain utility grey-ware pottery begins to appear, as well as thin walled black-on-grey painted ware; the bow and arrow replaces the spear and atlatl; and the bean comes to the Anasazi via trade with Central America. They begin to scatter over wider areas including both canyons and mesa tops, building small villages of two to three houses consisting of semi-subterranean pithouses, often with a small antechamber or small room built on the south or southeast side. Large, round, subterranean "kiva" prototypes are also built. By around A.D. 750 the settlements being to take on a more familiar, “typical” Puebloan feel. From here on, they are referred to as the Puebloans.

Pueblo I: c. A.D. 750 to 900

From this point on the periods of development get shorter. Several significant and obvious changes occur during the PI period: the flattening or deforming of the skull by strapping babies into cradle boards came into fashion; villages increase in size; great kivas are beginning to appear; many of the pithouse habitations are replaced by larger living rooms built together in room blocks on the surface, constructed with wattle-and-daub or crude masonry, adjoining walls are common; the wind deflector/ventilator was developed to ventilate the subterranean rooms; pottery styles are more distinct with the black-on-white becoming more differentiated from the gray utility wares, and red-ware pottery beginning to be produced in SE Utah; grey cooking pots began to show some refinement – the last few coils are not smoothed - leaving a banded effect on the neck; a significant change in settlement distribution occurs, large groups concentrate in some areas and abandon others previously inhabited; in some places irrigation systems including canals and reservoirs are constructed. They are highly dependent on agriculture by this time and are living year-round in the pueblos. During this period construction begins on the Chacoan Great Houses.

Pueblo II: c. A.D. 900 to 1150

The clustering of groups and development of large villages seems to gradually shift back to dispersed, smaller settlements. Many of the PII sites consist of five to ten living rooms built together as a unit pueblo, and the pithouses are entirely underground, becoming the kiva; usually built as a separate structure in front of the room block to the north or northeast; with the trash midden usually located to the SE of the complex. The grey, neck banded utilitarian pottery becomes corrugated over the entire surface of the pot, with fingerprints showing where each coil was pinched together. Small cliff granaries become common, often being built in nearly inaccessible locations. The Anasazi also begin to grow softer, flour corn, as opposed to the hard, shatter prone, flint corn. This seems to have altered the grinding technology, with the large, deeper trough shaped metates giving way to smaller flat slab metates without sides.

Pueblo III: c. A.D. 1150 to 1300

During the 1100s and 1200s the Anasazi began grouping together again into larger masonry villages; the unit pueblos were still occupied but many were built together into multi-story units with the kiva being enclosed within the room block. It was during this time that the great cliff dwellings of Mesa Verde in SW Colorado were built. The very elaborate, thick walled Mesa Verde Black-on-White pottery was produced during this period. Corrugated grey utility ware was still made and the Kayenta red-wares were still being imported into the region. Beginning in about A.D. 1250 the Anasazi began to move out of SE Utah for areas south in New Mexico and Central Arizona . By A.D. 1300 they had abandoned the San Juan River basin.