This document profiles three pioneering female microbiologists: Alice Catherine Evans, Rebecca Lancefield, and Lynn Margulis. It provides biographical details and highlights of their scientific contributions. Evans was the first female president of the Society of American Bacteriologists and worked at the USDA. Lancefield developed the serological classification of streptococcal bacteria and was the second female president of the society. Margulis developed the endosymbiotic theory of the origin of eukaryotic cells and organelles and was a distinguished professor who authored many publications.