The identification of geographical patterns in microbial distributions has begun to challenge purely ecological explanations of biogeography and the underlying principle of "everything is everywhere: but the environment selects". How did 'everything is everywhere' arise out of nineteenth century microbiology, and from Beijerinck's experimental and theoretical work in particular? What is the relationship of this principle to the plant and animal biogeography that flourished throughout this formative period of microbiology's history? Understanding Beijerinck's legacy for twentieth century microbial biogeography reveals issues that are still pertinent to contemporary discussions of microbial biodiversity and biogeography.