This paper describes the scope of the entire project and then presents findings from the initial stages of analysis of the relationship between population and the environment in counties of the US Great Plains region. Findings indicate that weather changes principally availability of soil moisture were related significantly to migration even after controlling for spatial autocorrelation. Most theories describe a one-directional path of change in which humans adapt to environmental conditions and changing technology. This study tests a variety of theories including models of spatial diffusion cultural diffusion political ecology and recursive models. It is posited that the dynamics over time of the spatial relationships between population and the environment are multidimensional. The structure of society and standards of living mediate the relationship between population and carrying capacity. Migration determines the size of population and density and migration is affected by the environment and infrastructure. Causality may shift or even reverse direction over time and space. The research strategy includes a long time-series analysis of county-level relationships detailed analysis of selected counties farm-level studies and sociocultural influences the history of farm families and communities and joint models of the environment social change and population. This paper begins with an analysis of short- or medium-term changes in weather and the role of migration in overall population change. The period 1930-40 is compared to the period 1970-80. Independent variables include the difference between the percent change in population and the percent change in population if migration had not occurred. Weather variables include the average monthly growing season precipitation from April through September and the ratio of the average monthly growing season precipitation to the average monthly growing season temperature.