If you do a Google search for "card catalog" it will likely return Pinterest-worthy images of antique furniture for sale — boxy, wooden cabinets with tiny drawers, great for storing knick-knacks, ...

The card catalog for the University of Virginia’s Alderman Library was once the only way to find needed books. Over four million cards cataloged each book’s location and from where it was donated.

Today, people use the antique wooden cabinets to store their knick-knacks. But these card catalogs once held the keys to a world of information. A new Library of Congress book explores their history.