Well, yes, it was the Centennial anniversary of the Declaration of Independence, but that never helped anyone find Seamus Heaney's translation of Beowulf in the library. While a librarian at Amherst College, Melvil Dewey patented and unveiled his system for classifying "all the world's knowledge" into ten main groups, with an infinite possibility of divisions within. A Decimal system! The Dewey Decimal System! (who knew it was patented? Not I.)
This is a pretty nifty system, which guides catalogers in assigning a number/shelf address to any item and ensuring that it will end up next to or near similar items with similar subject matters. All the American poetry is together! All the cookbooks are in a row! In the 1960s, many college libraries converted to the Library of Congress classification, but even in the 21st century, most public and school libraries in the United States still organize their material collections with Dewey numbers. Librarians can always help if you don't know exactly what the Dewey system is, or how it works (if you're curious you can go to the Wikipedia article, which explains it nicely), but it sure is handy.
Or if you'd rather see what finding Beowulf might be like in a library without Mr. Dewey's invention, jump into "The Confusing Library", a vintage sketch from The Two Ronnies. Note that Melvil Dewey was a librarian, not an architect :-)