Twain mentions four social classes in the novel starting from the top, we have the wealthy, aristocratic people represented by the Grangerfords. Mr. Grangerford was described as a 'well born' kind of person. There is a middle caste of white people. For instance, on page 15, "Why can't the widow get back her silver snuff-box that was stole? WHy can't Miss Watson fat up?'
The next rung down is a lower class of white people like Huck. The very last consists of African American people like his friend Jim.