I prefer Fretmentor's own history sections on the origin of not only the banjo but the guitar and mandolin. While I am biased since I am the author and researcher, I do so for the following reason: I footnote sources in my articles and do not plagiarize (and that includes photos). I have come across too many websites that appear to do no more than rephrase what is on the web.
Here is a link to Fretmentor's history tour
Re: Sweeney .. if you research the banjo you really have to dig deep to find original documentation to support the origin of the banjo and how it evolved into a five-string instrument (let alone who actually added the 5th string). Finding original, and substantive documents are like looking for a needle in the haystack. Sorry Kmando but that Swiss born North Carolina transplant you speak about is well read. While not discounting Sweeney, there were many west african slaves who should receive recognition about their contributions long before the minstrel artists. May I suggest you study the University of North Carolina archives on slave interviews as a starting point.
Fretmentor's history section is a work in progress and you might want to check back for updates. Feel free to contribute as well, as anything that supplements the banjo's (mandolin or guitar) origin and the artists who defined these instruments will definitely be beneficial to this site.