During its nearly 100-year history, the Chemistry Library at the University of Chicago and its librarians have responded to changes in the university and in society, including changes in the practice of librarianship, scientific publishing, chemical research, and higher education. A century of discussion about the benefits and shortcomings of departmental libraries has also appeared in the library literature. A review of this literature highlighted a set of issues that influence organizations in their decisions to support departmental libraries or to consolidate these branch libraries into centralized facilities. In the case of the University of Chicago's Chemistry Library, the relative importance of these various issues changed over time, and led to periodic changes in library services, physical facilities, and collection practices. Eventually, the traditional departmental library model gave way to changes in the institution and in scholarly publishing, creating a "tipping point" which led to the current centralization of the collections and services.