Visiting the National Institutes of Health (NIH) headquarters in Bethesda, Maryland, ten miles north of downtown Washington, D. C., is a lot like walking across the grounds of an elite research university, albeit with upgraded security.

Red brick buildings open onto rolling lawns. Small groups of people wander by, intent on conversation — about the human genome project, one imagines. A brightly lit cafeteria serves strong black coffee.

Although the campus is bursting with labs and research space, it is anchored by a massive library with a stately facade and a fascinating history. The US National Library of Medicine began in 1836 as a shelf of books in the Office of the Surgeon General and evolved to become the largest biomedical library in the world, concurrently housing millions of physical items and serving electronic data to millions of online users around the world.

“My fantasy holiday,” writer Mary Roach, author of the books Stiff, Spoof, and Bonk, has said, “is a week spent locked in the archives of the National Library of Medicine.”

Located in Ford’s Theater during the decades after Lincoln’s assassination, then occupying a spot on the National Mall, the library’s historic holdings were moved to Cleveland, Ohio, for a time during World War II to protect them from a potential attack by Hitler’s Third Reich. Moving to the NIH campus in the 1960s, the National Library of Medicine now stores its rare and valuable holdings in two intersecting worlds: analog and digital.