SW Culture Area
The Southwest Culture Area covers the southwestern United States and northern Mexico. It lies north of the Meso-American culture hearth, southwest of the Plains, south of the Great Basin and east of California.
It includes parts of southeastern Utah and California, southern Colorado, west Texas and northern Mexico. It covers almost all of Arizona and New Mexico.
Geographic regions are defined by their landforms and climate; plant and animal communities; range of human cultural expressions, dominant cultures, languages, and histories; and in contrast with one another. Since things change — particularly human cultures and histories, the boundaries of a geographic region change through time and with changes in our perspectives.
For example, the map above, based on categories in the Handbook of North American Indians, depicts the SW Culture Area. Today, the modern day Southern and Ute Mountain Ute people occupy southwestern Colorado. They are classified with Great Basin cultures so the Ute and southwestern Colorado are not part of the Southwest Culture Area on the above map.
However if we were to look at dominant groups near the middle of the last millennium, the Anasazi culture area extended into much of southwestern Colorado and all of southern Utah and shared the area with the Ute.
Our geographic definitions of culture area need to be sensitive to time and include the concepts of culture period and cultural identity.
By many definitions the Southwest includes the Mexican states of Chihuahua, Durango, and some include the peninsula of Baja California. It has been given several different names: the Greater Southwest (Beals 1932), Oasis America (Armillas 1969; Kirchhoff 1943), Aridoamerica (Kirchhoff 1954), La Gran Chichimeca (Di Peso 1974), El Noroeste Mexicano, and the International Four Corners (Minnis 1989). None of these names are entirely satisfactory or uncontroversial.
As an organizing principal, the culture area is a useful categorization for understanding a region. But it forces the usually empirical archaeologists to consider cultural factors that may not be directly reflected in the material record such as language, history, cultural belief and identity.
Some resist this movement toward considering their subject as a humanistic science and want to restrict archaeological study to compiling trait lists of material culture and limit explanations to mere description of artifacts.
As graduate students in the 1970's we were discouraged from reading ethnographies of the descendants of the people who's remains we were studying and restricted to empirical description of tangible artifacts. The synthetic theory that could flesh out our interpretation of our findings to provide insight and deeper understanding of the human condition was disparaged as "soft science" and remained unarticulated and inchoate.
An excellent contrast of the two approaches can be found in University of Minnesota archaeologist Janet Spector's book, What this Awl Means, where she contrasts the description of an awl as a woman's working tool, the handle of which was etched in a way to keep a count of the things she manufactured for her family — the number of hides prepared and mocasins sewn, etc. It was a personal record of her achievements and of the sources of meaning in her life — an artifact understood and appreciated by her descendents (some of whom worked on the excavation crew) with the empiricist's approach that limited the description of the same awl according to its dimensions, composition, and use wear markings on its surface.
This limitation on the focus of archaeological science echoes a debate in geology that occurred in the 19th Century, highlighted by Charles Darwin:
Darwin On the Need for Theory
"About thirty years ago there was much talk that geologists ought only to observe and not theorize; and I well remember someone saying that at this rate a man might as well go into a gravel-pit and count the pebbles and describe the colours. How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service!"
(Charles Darwin in F. Darwin and A. C. Seward, More Letters of Charles Darwin, London: Murray, 1903: 195 
The upshot of the debate is that we need synthetic theory to make sense of our subject matter. Culture areas are theoretical constructs which help us understand peoples and places. The debate over their boundaries and who and what get included and excluded give us insights and deeper understanding.
Handbook of North American Indians, Vol. 9, Southwest, 1979. Alfonso Ortiz, vol. ed. Smithsonian Institution, Washington, D.C.
Armillas, P. 1969 The Arid Frontier of Mexican Civilization. Transactions of the New York Academy of Sciences, Series II, 31(6):697-704.
Beals, R. L 1932 The Comparative Ethnology of Northern Mexico before 1750. Ibero-Americana 2.
Darwin, Charles 1903  in F. Darwin and A. C. Seward, More Letters of Charles Darwin, Murray, London.
Di Peso, C. C. 1974 Casas Grandes: A Fallen Trading Center of the Gran Chichimeca, vols. 1-3. Amerind Foundation Series No. 9. Amerind Foundation, Dragoon, Arizona, and Northland Press, Flagstaff, Arizona.
Kirchhoff, P. 1943 Mesoamerica: sus límites geográficos, composición étnica y sus caracteres culturales. Acta Americana 1:92:107.
1954 Gatherers and Farmers in the Greater Southwest: A Problem in Classification. American Antiquity 29:529-550.
Minnis, P. E.1989 "The Casas Grandes Polity in the International Four Corners". In The Sociopolitical Structure of Prehistoric Southwestern Societies, edited by S. Upham, K. G. Lightfoot, and R. A. Jewett, pp. 269-305. Westview Press, Boulder, CO.
Spector, Janet D. 1993 What this Awl Means. Minnesota Historical Society Press, Mpls. MN.