The proliferation of hospital libraries since World War II has created a generation of librarians who take for granted the existence of libraries in hospitals. A literature review for the first half of the twentieth century presents a picture of uncertainty and struggle for identity for the hospital library. Then as now, hospital libraries reflect the institutions within which they operate. A brief history of the development of the American hospital provides a context for describing the various roles that the hospital library has played within its parent institution during the twentieth century. Some personal reflections on working in a hospital library are also presented.