Answer: Project Gutenberg

While it may not be the biggest digital library today, Project Gutenberg does have the distinction of being the first. Back in 1971, decades before digital books and carrying them around on ebook readers would enter the public consciousness, Michael Hart, then a student at the University of Illinois, began work on digitizing books for public use.

Why take on such a project, especially in an age when computers were bulky and difficult to use boxes owned by universities and governments, and not found in homes (let alone so small that we could carry them around with all of our books loaded on them)? Hart believed that a future would come when computers would be ubiquitous and believed it important that books and historical documents be preserved and shared.

Over the years, Hart recruited a team of volunteers to help him digitize more books and the Project Gutenberg collection now houses 65,405 books and documents (as of May 2021) available in a wide range of formats like text files, PDFs, and even formats for popular ebook readers.