Science in general, and microscopy in particular, lagged far behind Europe in early 19th century America. Jacob Bailey was one of the very few American microscopists. In eulogies he was called 'the Ehrenberg of America' and 'the founder of microscopical research'. He was a major figure in the scientific community of America in his time and instrumental in promoting microscopy and the study of microscopic organisms. His name maybe familiar to specialists who focus on diatoms, foraminifera, or radiolaria. However, Bailey's important contributions to protistology have received very little attention and he is rarely mentioned in histories of protistology. Here Jacob Bailey's life, his protistological works, as well as his roles in the development of microscopy in America and the 19th century debate over life in the deep sea, are reviewed.