Historical Anthrax Incidences between 1915–1944 in Texas/Louisiana and The Dakotas/Nebraska/Iowa. Adapted from Stein (1945, ). Darker colors represent severe outbreaks and the lighter colors represent sporadic outbreaks. The blue and green colors were used to illustrate that two distinct genotypes (Western North America (WNA) and the Ames sub-lineage) have been indentified in "modern" isolates from these two regions. The counties bordered in yellow in Texas indicate counties where documented incidents of anthrax have occurred between 1974 and 2000. The numbers 1–4 indicate the counties in which the original Ames strain, 2 bovine samples and a goat sample have been analyzed by current genotyping methods as belonging to the Ames sub-lineage. The molecular analysis of more than 200 isolates from North and South Dakota indicates a pre-dominance of the sub-lineage WNA in this region. The gray colors indicate moderate to sparse outbreaks in the states adjoining the Dakotas and Texas.