The United States Geological Survey's PRISM2 climate modeling software has been used to create a climate change simulation for the continental US during the middle Pliocene warm period (approx. 2 million years ago). The rationale for creating such a model is (1) to better understand the nature of and controls on climate change during an interval of sustained warmth and reduced climatic variability and (2) to assess the validity of the general circulation model (GCM) approach by comparing model predictions with empirical measurements of climatic variables based on a variety of paleontological and sedimentological observations. These simulations suggest that the middle Pliocene was, on average, warmer, less seasonal, and wetter than the modern US climate with a marked absence of freezing over the central and southern Plains. These retrospective changes appear to have been primarily driven by reduced snowfall and the effect of a lower Rocky Mountain Range on patterns of atmospheric circulation. While these predictions appear to be in broad agreement with independent paleontological and geological observations, the model seems to underestimate rainfall levels in central and southern regions.