The Postclassic period (AD 900-1521) in Mesoamerica marked an era of significant social change. During this period of time in the American Southwest, Puebloan cultures also engaged in their own major social transformations. A central concern of archaeologists has been to seek connections between these two broad regions and these social changes, whether in material culture or ideology, that help to clarify the nature and extent of long-distance interaction and integration of people in the past.

This dissertation primarily examines the rise of two major cultural traditions in Northwest Mexico: the Casas Grandes and Aztatlán cultures. To understand these cultures, and the nature of their social, political, economic, and religious organization, is to enable scholars to understand how social change on a continental scale was intertwined and interrelated. This work argues that the rise of the Aztatlán and Casas Grandes cultures was primarily due to the expansion of a new worldview and an entire system of beliefs and socio-political organization, with local manifestations, that was centered upon the Flower World complex, a cosmological framework that penetrated to the core of every aspect of the life of an individual and the community. The adoption of this religious complex, a veritable world religion centered upon the sun and a floral paradisal realm, was at the heart of nearly every major social change in Northwest Mesoamerica and the American Southwest after AD 900. This belief system continues to play a significant role in social change to the present day.

Drawing from the spectrum of academic disciplines, this work reflects a broadly humanistic approach in the comparative study and synthesis of data from archaeology, ancient and contemporary religion and symbolism, literature, arts, and native oral histories. Thus, it is uniquely suited for the goal of reconstructing a balanced social history of past and present culture change in the American Southwest and Mesoamerica. The goal of this research is to construct a new conceptual framework for scholars to obtain a better understanding of the mechanisms by which religious beliefs were transmitted and transformed in the past in local and regional cultural contexts across time and space.