In the nineteenth and early twentieth centuries public libraries used annual reports to inform the public and one another about new services and managerial approaches. Because librarians filled reports with statistics, narrative, and professional philosophy and exchanged them throughout the country, nearby collections of reports can provide rich and accessible evidence for institutional, social, and cultural history studies. However, starting in the 1920s, library reports began to emphasize themes rather than departmental details, and librarians increasingly communicated through journals. Thus some libraries ceased collecting institutional publications. Although today's reports are suitable for public relations purposes, historians should be concerned about their limited content and distribution.