Dates for PIII are about A.D. 1100 to 1300. During PIII, there is a tendency for Anasazi sites to become larger and incorporate many more numbers of individual masonry rooms into a single structure. It is during PIII that aggregations of rooms become very large, and (excluding Chaco) there is the first good evidence of social complexity. PIII trends can be summarized as follows:

Construction of multi-room, often multi-story cliff dwellings in numerous areas, including the Mesa Verde area in Colorado, and the Kayenta area in northeastern Arizona. There is some reason to believe that cliff dwellings were used for defensive purposes in some areas, but in others this does not appear to have been the function.

There are new developments in PIII regarding agricultural strategies. This can be seen in the adoption of a variety of stone features to control the flow of surface runoff or conserve soil moisture, e.g., rock alignments, bordered gardens, check dams, and terraces. There seems to be a more intensive effort placed in the cultivation of individual fields, probably reflecting the need to extract more agricultural produce from more locations immediately surrounding the larger pueblos.

Some PIII settlements are considerably larger than any previous settlements. In the Mesa Verde area, there are large cliff dwellings that incorporated several hundred people, and in a few other non-cliff dwelling sites, the people living in a single village may have exceeded 1,000. The number of people participating in the Mesa Verde cultural system is estimated at several thousand. Clearly, during PIII there are new social forms that involved integration of far more people than ever before. There are a number of human burials during PIII that contain large quantities of funerary objects, indicating that some individuals had accumulated a great deal of prestige and status, and a number of social roles. Thus, we may infer that these individuals consituted a form of social "elite," and probably had a measure of political and religious leadership that did not exist in earlier time periods. Following the collapse of the Chaco system, it appears that many regions adopt their own social, relgious, and political systems that in some ways mirror the Chaco architectural forms (e.g., great kivas), but are distinct and have their own regional flavor.

There is continued elaboration of ceramic production, with regional ceramic design styles arising that are quite distinctive. In many areas, it is clear that there is ceramic specialization, with a few artisans producing pots for export. There is a tendency for the gray corrugated pottery to decline in quality, but other forms, especially the black-on-white types, achieve their finest expression. Toward the end of the PIII period, there appear polychrome pots pained in orange, red, black, and white. These form the basis for many of the later PIV polychrome pottery traditions.

Toward the late 1200s, many PIII cultural systems are abandoned. The entire area surrounding Mesa Verde, most of the Kayenta Anasazi area, Flagstaff, and many more regions are mostly or completely abandoned. In some areas there is a prolonged period from about A.D. 1276 to 1299 that is referred to as the "Great Drought." It is debated whether or not this drought would have been severe enough to cause abandonments of the scale that is known, but the late 1200s are a time of great cultural change and population movement. Around 1300, we see the movement of people into a few locations and the beginning construction of what later (during PIV) become extremely large pueblo towns.