The evolutionary and ecological forces that govern microbial biogeography remain poorly characterized. We examined the biogeography of Streptomyces at regional spatial scales to identify factors that govern extant patterns of microbial diversity within the genus. Streptomyces are spore forming filamentous bacteria that are widespread in soil and are a predominant source of antibiotics. We applied population genetic approaches to analyze geographic and genetic population structure in six phylogroups of Streptomyces identified from a geographically explicit culture collection. Streptomyces strains were isolated from soils associated with perennial grass habitats sampled across a spatial scale of more than 5,000 km. We find that Streptomyces allelic diversity correlates with geographic distance and that gene flow between sites is constrained by latitude. In addition, we find that phylogroup nucleotide diversity is negatively correlated with latitude. These observations are consistent with the hypothesis that historical demographic processes have influenced the contemporary biogeography of Streptomyces.