The name assigned to the culture was derived from the Mogollon range of mountains which lies in the district in which many of the chief ruins have been found. The principal sites which have been excavated lie in the valleys of the San Francisco and Mimbres rivers in west-central New Mexico, in the Forestdale Valley of Arizona, and in southeastern Arizona. It is probable that, as further work is done, the geographical range of the culture may be further increased. The area in which Mogollon remains have already been found is a large one, equally as extensive as the Basketmaker. Proponents of the theory that the Mogollon is a basic culture point out that it is an important fact that it has geographic substance.[59] It would be pleasant to be able to divide the Mogollon into clear-cut periods with established dates and full lists of the traits which characterize each stage. Unfortunately, this cannot be done. It has been possible to determine, in a general way, the stages of cultural development in certain sites in New Mexico where there was some degree of uniformity. In other areas, however, conditions were different, and it is impossible to say that at any given time all the Mogollon people had the identical type of culture, although there are enough points of similarity to permit us to assign them all to the same general group. It seems probable that, as further work is done, separate regional chronologies will be worked out as has been done for the Pueblo sequence where we recognize significant differences between cultural centers such as Chaco, Mesa Verde, and Kayenta.[59] For the present these regional variations add to the complexity of the problem. A further complication arises from the fact that even those who recognize the Mogollon as a basic culture feel that it is only during the earliest times that they are dealing with a relatively pure culture, and that after 700 or 800 A. D. the Mogollon Culture was beginning to be assimilated by the Anasazi, and that there were also Hohokam influences. Dates for Mogollon sites are very difficult to determine, for only a few tree-ring dates are available. One find tends to suggest a considerable antiquity for the culture. At Snaketown, in the earliest Pioneer level, was found a polished red ware, which, through petrographic analysis, has been shown to contain materials not used at Snaketown, but identical with those of wares from Mogollon sites.[31]^d This pottery is better made than the early Hohokam pottery and would suggest that the Mogollon people had been making pottery for some time prior to the beginning of the Christian era. Another possibility which has been suggested is that both they and the Hohokam obtained pottery from some other source which has not yet been identified.[99] BLUFF RUIN[58]