In the middle section of The Adventures of Huckleberry Finn, what obstacles lay in Huck’s path of adolescence towards maturity?
In many ways, the middle of the novel is dominated by the meeting of and interaction with the duke and the king. After crashing with the steamboat and spending some time with the Grangerfords and his having to decide whether to take sides or to act in the feud or try to stay on the sidelines. After seeing his friend Buck die, Huck decides again to move on down the river with Jim. His pain at seeing Buck getting killed as well as the trouble between the two families and the outsider's perspective that lends an absurdity to it is one of the things he faces.
The entrance of the duke and the king provide an enormous obstacle because they walk in and take over positions of authority relegating Huck and Jim to the position of taking orders rather than being free to make their own decisions. This loss of power and freedom is not conducive to growth on the part of Huck and in many ways he is "held down" by the decisions of the duke and the king.
Towards the end of the middle section or the beginning of the end, the decision that Huck makes to seek Jim's rescue is perhaps the indication that he has now left the obstacles behind and is moving decisively out of adolescence.