The William H. Welch Medical Library was founded in 1929 with the merger of three libraries, namely, the library of the School of Medicine, the library of the School of Hygiene and Public Health, and the library of the Johns Hopkins Hospital. Engendered by the dreams of Johns Hopkins University bibliophiles, such as founding Hopkins physicians William Osler, William Stewart Halsted, Howard Kelly, and William Henry Welch, the library flourished and expanded. At the same time as the founding of the central medical library, the Institute of the History of Medicine collection was established in the Welch Library building, with William H. Welch as its first director. Innovative leadership led to many exciting projects, such as the Welch Indexing Project, which was a prototype for the National Library of Medicine's medical subject headings, and the establishment of a laboratory for research into the application of information technologies to knowledge management. The Welch Library enters the 21st century as a dynamic library committed to the continuing delivery of information services, as well as ongoing research into the development of library services for the coming 100 years.