This dataset was used in the USGS Gap Analysis Project (GAP) species habitat distribution modeling process. Processing constraints made it impractical to model the species habitat distributions across the full conterminous U.S. in one model. The modeling regions were used to stratify the lower 48 states into modeling extents that could be efficiently used in our workflow. The regions were based on grouping of the map zones developed for the National Land Cover Dataset production and were designed to partition the full extent into the minimal number of regions while maximizing the homogeneity of habitats within a region. Two versions of each modeling region were created one in which a buffer was applied to remove boundary issues when calculating metrics based on neighborhoods, and a version used to clip the final model output for that region tightly to the region boundary. These raster data have a 30 m x 30 m cell resolution. GAP used the best information available to create the modeling regions ancillary data; however GAP seeks to improve and update these data as new information becomes available.