The archaeology of southwestern Colorado from A.D. 900 to 1300 presents a number of interesting problems, including population aggregation and abandonment. We report on an on-going project, implemented using the modeling libraries of Swarm, to model the settlement dynamics of this region, treating households as agents. Landscape detail includes an annual model of paleoproductivity, soils, vegetation, elevation, and water resource type and location. Individuals within households reproduce and die; households farm, relocate, and die; children within households marry and form new households. Household location is responsive to changing productivity (depleted in some scenarios) and, in some scenarios, water resources. Comparison of simulated settlement with the archaeological record highlights changes in the settlement and farming strategies between Pueblo II and Pueblo III times, including the increasing importance of water and sediment-control, and other alternatives to extensive dry farming. Our results suggest that degradation of the dry-farming niche may have contributed to these changes. This project began with a desire to understand why, during certain times in prehistory, most Pueblo peoples lived in relatively compact villages, while at other times, they lived in dispersed hamlets (Cordell et al. 1994). Our approach to this problem is based on a thread of accumulating research begun in the early 1980s when a dissertation from the University of Arizona by Barney Burns (1983) showed that it was possible to retrodict potential prehistoric maize yields in a portion of Southwest Colorado by combining prehistoric tree-ring records with historic crop-production records of local farmers. A few years later, Kohler et al. (1986; see also Orcutt et al. 1990) simulated agricultural catchment size and shape in a northern portion of the present study area, to arrive at the suggestion that avoiding violent confrontation over access to superior agricultural land was a major force in forming the villages that appeared in this area in the late A.D. 700s and again in the mid-800s.