There were books before Gutenberg printing press, just as I'm sure there were digital archives before Project Gutenberg. Interestingly they have both served the same function; the printing press marks the popular dissemination of the book and Project Gutenberg marks the first of the free, large-scale digital archives. For those manning the presses in those early days the work was dangerous and messy. I imagine the early work of Project Gutenberg was characterized by the tedium of old school data entry and, later, finicky scanners. Beyond its early creation date (1971). I think the sheer amount of effort invested by so many volunteers is what makes this archive noteworthy. It was started and persevered during the years when digitization was just plain hard.
So forty year later, Project Gutenberg has ten affiliated partners internationally (such Project Gutenberg Australia) and over 38 000 works available for free download. They provide ebook editions of public domain materials in many translations and usable formats. The more material that moves out of copyright, the larger the collection grows. If something is considered a classic work, it is probably available there.