The Public Library of Cincinnati and Hamilton County now has a very rare and amazing offering for all of us lovers of all things Sam Clemens. A total of seven personal letters written by Twain himself are now on display, and are available to be read and downloaded at the library's website.
Ranging from 1870 to 1903, the letters are in Twain's own handwriting, to a variety of different recipients. They can be viewed at the website, and downloaded in full-color, PDF format. This is a unique opportunity, and one I suggest you take advantage of.