United States National Library of Medicine

The U.S. National Library of Medicine (NLM) is the world's largest medical library, part of the National Institutes of Health in Bethesda, Maryland, and a major provider of biomedical information and databases.

The National Library of Medicine (NLM) is a federal institution that collects, organizes and provides access to biomedical information for researchers, clinicians, students and the public. Located on the National Institutes of Health (NIH) campus in Bethesda, Maryland, it is widely recognized as the largest medical library in the world and a central hub for health data and literature.

Collections and facilities

NLM maintains extensive physical and digital collections that include books, historical prints, journals, manuscripts and a vast repository of electronic content. Its holdings span contemporary biomedical research, clinical literature, historical medical works and specialized databases. The library supports preservation, digitization and long-term access initiatives to make resources available beyond the physical stacks.

Major services and resources

PubMed / MEDLINE: searchable citation databases for biomedical literature.
PubMed Central: a free archive of full-text articles.
ClinicalTrials.gov: a registry and results database for clinical studies.
MeSH: the Medical Subject Headings controlled vocabulary used for indexing.
NCBI: the National Center for Biotechnology Information, housed at NLM, provides bioinformatics tools and genomic databases.

These platforms make NLM a primary provider of searchable, standardized biomedical information used worldwide by health professionals and researchers.

History and development

The institution traces its origins to the library of the U.S. Army Surgeon General's Office established in the 19th century. Over time it evolved into a national library with federal support and expanded services, embracing digital technologies and networked information systems during the late 20th and early 21st centuries.

Beyond collections, NLM engages in informatics research, develops standards, offers training and runs outreach to improve health information access. Its services are cited widely in clinical decision making, research, education and public health, making it a cornerstone of biomedical information infrastructure in the United States and internationally.