 In 1894 he was appointed curator of the department of botany of the Field Museum of Natural History; from 1897 to 1923 he was professor of medical botany at the Chicago Homeopathic Medical College.He was also lecturer on botany at the University of Chicago.Millspaugh carried on explorations in the West Indies, Brazil, and other parts of South America, and was the author of "American Medical Plants" (1887); "Flora of West Virginia" (1891); and many articles in scientific and popular journals.