Melvil Dewey was a librarian in the 19th century who invented the Dewey Decimal System to better organize books in libraries. Previously, books were organized by size and color, making it difficult for patrons to find materials on their own. Dewey's system categorized all books into 10 main subject areas using numbers from 000 to 900, allowing anyone to browse shelves and find relevant books without needing to ask the librarian directly. This made information much more accessible to library patrons.