This study examines political evolution and archaeological data, producing a sociopolitical model of the rise, florescence, and decline of the Chaco Phenomenon.In the tenth century AD, a remarkable cultural development took place in the harsh and forbidding San Juan Basin of northwestern new Mexico. From small-scale, simply organised, prehistoric Pueblo societies, a complex and socially differentiated political system emerged which has become known as the Chaco Phenomenon. This study combines information on political evolution with archaeological data to produce a sociopolitically based model of the rise, florescence, and decline of the Chaco Phenomomenon.In the tenth century AD, a remarkable cultural development took place in the harsh and forbidding San Juan Basin of northwestern new Mexico. From small-scale, simply organised, prehistoric Pueblo societies, a complex and socially differentiated political system emerged which has become known as the Chaco Phenomenon. This study combines information on political evolution with archaeological data to produce a sociopolitically based model of the rise, florescence, and decline of the Chaco Phenomomenon.In the tenth century AD, a remarkable cultural development took place in the harsh and forbidding San Juan Basin of northwestern New Mexico. From small-scale, simply organized, prehistoric Pueblo societies, a complex and socially differentiated political system emerged that has become known as the Chaco Phenomenon. This study combines information on political evolution with archaeological data to produce a sociopolitically based model of the rise, florescence, and decline of the Chaco Phenomenon.1. Introduction; 2. The Chaco Phenomenon: background and history of research; 3. Sociopolitical complexity and the Chaco system; 4. Routes to sociopolitical power; 5. Previous explanations for the Chaco Phenomenon; 6. Relations of power, labor investment, and the political evolution of the Chaco system; 7. Summary and new directil£Q