The central theme of US History that is of course explored in this excellent novel is that of slavery and the relationship between whites and blacks. This novel was written at a time when slavery was still rife in the South, and the relationship between whites and blacks was characterised by a massive power imbalance. We see this modelled in the emerging friendship between Jim and Huck. Note how in Chapter Ten Huck treats Jim as though he were a source of fun rather than another human being. He places a dead snake in Jim's blanket, thinking it will be a good joke:
I killed him, and curled him up on the foot of Jim's blanket, ever so natural, thinking there'd be some fun when Jim found him there. Well, by night I forgot all about the snake, and when Jim flung himself down on the blanket while I struck a light the snake's mate was there, and bit him.
Huck treats Jim in a way that reflects the norms of his day at this stage of the novel: he does what he wants without thinking of the consequences. He certainly does not own up to what he did and he doesn't even say that he is sorry. This would have been typical of the attitudes of the day. However, as time goes by and they spend more time together, Huck comes to see Jim more and more as a human being. He "humbles himself to a nigger" and finaly even is willing to forego heaven to help Jim escape. Therefore this novel can best be related to the theme of slavery in US History and changing attitudes.