The Bancroft houses, among other gems, the papers of Mark Twain, a copy of Shakespeare’s First Folio and the records of the Donner Party. Its small public exhibits of historical Californiana include the surprisingly small gold nugget that sparked the 1849 Gold Rush. To register to use the library, you must be 18 years or older (or a high school graduate) and present two forms of identification (one with a photo). The registration desk is on your way in.