ThePecos Classification is a chronological division of all knownAncestral Puebloans into periods based on changes inarchitecture,art,pottery, andcultural remains. The original classification dates back to consensus reached at a 1927archæological conference held inPecos, New Mexico, which was organized by the United States archaeologistAlfred V. Kidder.

The original Pecos Classification contained eight stages of Southwestern prehistory, but it did not specify dates.

1. Basketmaker I, or Early Basketmaker II
2. Basketmaker II, or Late Basketmaker II
3. Basketmaker III, or Post-Basketmaker
4. Pueblo I Period, or Proto-Pueblo
5. Pueblo II Period
6. Pueblo III Period, or Great Pueblo
7. Pueblo IV Period, or Proto-Historic
8. Pueblo V Period, or Historic

Although the original classification has been significantly debated and sometimes modified over the years, the split intoBasketmaker and Pueblo period still serves as a basis for discussing the culture of theAncestral Puebloans of theFour Corners area. The following classification is based in part of the Revised Pecos Classification for the Mesa Verde Region.

The pre-Ancestral Pueblo culture that moved into the modern-daySouthwestern United States after the big game hunters departed are calledArchaic. Little evidence for extensive habitation before 8000 BC exists. From evidence nearNavajo Mountain, they werenomadic people,hunter-gatherers traveling in small bands. They gathered wild foods when inseason, and hunted with stone-tipped spears,atlatls, anddarts. Game includedrabbits,deer,antelope, andbighorn sheep.

The original classification postulated aBasketmaker I Period which was subsequently discredited due to lack of physical evidence. It was combined with theArchaic Period.

This period was calledOshara tradition. There was a trend toward a sedentary lifestyle, with small-scale cultivation of plants beginning 1000 BC.

The early Ancestral Pueblo camped in the open or lived in caves seasonally. During this period, they began to cultivate gardens ofmaize (flint corn in particular) andsquash, but nobeans. They usedmanos andmetates to grind corn, and the women made baskets for numerous uses.

The people constructed primitive storage bins,cists, and shallowpit-houses. At this stage, evidence suggests that the beginning of a religious and decision-making structure had already developed.Shamanistic cults existed, andpetroglyphs and other rock art indicate a ceremonial structure as well. Groups appear to be increasingly linked into larger-scale decision-making bodies.

Deep pithouses were developed, along with some above-ground rooms. The bow and arrow replace the atlatl and spear. Plainbisque and some painted black-on-white pottery is made. Cultivation begins of beans, available due to trade from Central America, and edible due to slow cooking in pottery vessels. Wildamaranth andpinyon pine were also staples. People of this period may have domesticatedturkeys.

The prototypekivas were large, round, and subterranean.

ThePueblo I Period saw increasing populations, growing village size, social integration, and more complicated and complex agricultural systems typified this Period. The construction and year-round occupation of pueblos begins; the people constructed reservoirs and canals to deal with scarce and irregular water resources. Large villages and great kivas appear, though pithouses still remain in use. Above-ground construction is ofjacal or crudemasonry. Plain graybisque predominates in pottery, though some red bisque and pottery decorated in black and white appears.

By AD 1050,Chaco Canyon (in present-dayNew Mexico) was a major regional center, with a population of 1,500–5,000 people. It is surrounded by standardized planned towns, orgreat houses, built from the wood of more than 200,000 trees. Thirty-foot-wide (9.1 m)roads, flanked byberms, radiate from Chaco in various directions. Small blocks of above-ground masonry rooms and a kiva make up a typicalpueblo. Great kivas were up to 50–70 feet (15–21 m) in diameter. Pottery consists of corrugated gray bisque and decorated black-on-white in addition to some decorated red and orange vessels. The people imported shells andturquoise from other cultures through trading.

During the 12th century, populations began to grow after a decline at the end of thePueblo II Period. More intenseagriculture was characteristic, withterracing andirrigation common.

Settlements consist of large pueblos, cliff dwellings, towers and turkey pens. Most villages in the Four Corners area are abandoned by AD 1300. The distinction between theHohokam and Ancient Pueblo people becomes blurred.

Typically, large pueblos are centered around aplaza. Socially, this was a period of more conflict than cooperation, which is thought to have led to abandonment of settlements at Mesa Verde. The people began makingkachinas for religious and ritual purposes. Plain pottery supplants corrugated. Red, orange and yellow pottery is on the rise as the black-on-white declines.Cotton is introduced and grown as a commodity.

The Puebloans are joined by other cultures. As early as the 15th century, the Navajo were in the process of migrating into the region from the north. In the next century, theSpanish colonists first came in the 1540s from the south.

The Spanish dominate and take over sites such as theAcoma Pueblo. Their arrival sends Pueblo subcultures underground.

• Mesa Verde National Park
• Canyons of the Ancients National Monument
• Bandelier National Monument
• Chaco Canyon inChaco Culture National Historical Park
• Canyon de Chelly National Monument
• Gila Cliff Dwellings National Monument
• Keet Seel inNavajo National Monument
• Chimney Rock National Monument

• List of dwellings of Pueblo peoples
• Hohokam
• Hopi
• Tiwa
• Zuni people
• John Wesley Powell
• Richard Wetherill
• Antiquities Act

• Catherine M., and H. Wolcott Toll. "Deciphering the Organization of Production in Chaco Canyon (Organization of Production at Chaco Canyon conference papers)."American Antiquity 66.1 (Jan 2001): 5.
• Kidder, Alfred V. (1927). Southwestern Archaeological Conference.Science 66: 489-91.
• Kidder, Alfred V. (2000 ed.) "An Introduction to the study of Southwestern Archaeology". Yale University.ISBN 0-300-08297-5