I responded to Jules off-forum. For anyone interested in study at the Huntington, be sure to allow time to get accredited there, especially if you are an Independent Scholar. The website for accreditation is 
https://aeon.huntington.org/aeon.dll?Action=10&Form=79


 Pay special attention to the application instructions. Applications will be considered incomplete and will not be processed without all the required components.



It does not appear they have a great deal on Twain himself, but there is material in Nevada Territorial friends such as John W. North



Bob Stewart