On a summer day in 1971, Michael Stern Hart typed the U.S. Declaration of Independence into his computer and shared it freely online via the University of Illinois at Urbana-Champaign.
That moment was the beginning of Project Gutenberg.
As of today, Project Gutenberg contains 44,847 books and texts in the public domain that can be searched via keyword, title or author. I’ve already written about finding a book mentioning one of my ancestors. This is a great way to find out context about various time periods or simply find some great texts to download to your electronic book reader.
Visit the site for your own searches at http://www.gutenberg.org/.