In the 1880s, bacteriology started to become an identifiable discipline of science as it separated from established fields of medicine such as pathology, histology and microscopy. It was during this period that Philadelphia medical students traveled to Europe to learn more about this new specialty and brought this knowledge back to the city. This first generation of bacteriologists established crude laboratories, and encouraged lectures in bacteriology to be included in the medical school curriculum. The first part of this book focuses on the people and institutions that played a significant role in establishing bacteriology in Philadelphia. A second generation of bacteriologists contributed to the formation of academic departments at medical schools, research institutes and pharmaceutical companies. In 1920, the formation of a branch of the Society of American Bacteriologists in Philadelphia set the stage for recording and documenting the evolution of bacteriology into microbiology with its many sub-specialties. This book attempts to summarize this evolution as it progressed in the Philadelphia area with an emphasis on the role of Eastern Pennsylvania Microbiology organization played in establishing Philadelphia as a center for teaching and research in this important area of science.