Huckleberry Finn features several different dialects. Twain makes this clear in the detailed “Explanatory” he includes at the beginning of the book:
In this book a number of dialects are used, to wit: the Missouri Negro dialect; the extremist form of the back-woods Southwestern dialect; the ordinary ‘‘Pike County’’ dialect; and four modified varieties of this last. The shadings have not been done in a haphazard fashion, or by guesswork; but painstakingly, and with the trustworthy guidance and support of personal familiarity with these several forms of speech.
In the “Explanatory” at the beginning of the book, Twain establishes that he intentionally studied and tried to replicate the “Missouri Negro dialect,” as seen in the way that the character Jim speaks. (Note that "Negro" is now considered an outdated and offensive way to refer to Black people.) The nature of Jim's dialect is exemplified in an emotional conversation with Huck:
Unlock with LitCharts A+“My heart wuz mos’ broke bekase you wuz los’, en I didn’t k’yer no mo’ what become er me en de raf’. En when I wake up en fine you back agin’, all safe en soun’, de tears come en I could a got down on my knees en kiss’ yo’ foot I’s so thankful.”