sights a small shanty and peers in the window. Knitting in the candlelight is a middle-aged woman, who is a stranger to Huck, who narrates,

Now this was lucky because I was weakening. I was getting afraid I had come; people might know my voice and find me out.

So, hoping to obtain some information, Huck enters the town. to discover if anything has been said about him and Jim. Because he is in conflict with citizens, Huck has to be very cautious.  In this chapter, then, the essential problem revolves around Pip, who harbors a slave, and cannot afford to have this condition discovered. This conflict is stated as Man vs. Society.

How can you narrow it down??! Well, the conflict of social inequity is certainly at the forefront of this novel. The theme of justice certainly ties into this, as well. The Widow Douglas tries to instill christian and family values in Huck, yet she owns Jim and is treated as property. Ironically, Jim has the only true family and morally conscious family in the novel. Huck struggles with his own feelings of right and wrong on this issue, at times understanding the injustice of owning human beings, but breaking the law in helping Jim escape.

I agree that it would tough to label just one major conflict - I would add to the above answers the individual vs. society.  This conflict is seen throughout the book in various circumstances.  Huck choosing to help free Jim, Jim's escape, the attempted lynch of Col. Sherburn, the King and Duke's scams against the towns they entered. etc.  One of Twain's purposes was to point out the hypocrisies in society, and he does this through this conflict.

The main conflict of Huck Finn is his struggle with his conscience. He has been raised with a certain set of values, and he struggles with those values when he goes against them. For example, when he helps Jim escape to freedom, he has been raised to believe that it's wrong to help a slave escape. He doesn't realize he's taken a stand against a society that condones enslaving others. He just feels he's "done wrong" because he didn't follow the beliefs that he's been taught.

You only want one? Then I'd say it is between forces that support civilization and forces that fight it. What makes the novel great, though, is that these are presented in such a complex and shifting fashion. At times Huck actively fights against being civilized; at times his great heart and his sympathy for Jim and others is the very soul of civilization. Likewise, stealing Jim is, technically, a crime, and an assault on American laws--but helping him be free fulfills the larger spirit and dream of American civilization.

There are many conflicts in this novel, so I believe it is a matter of opinion as to which is the main conflict. Some would argue that the main conflict is Huck vs society, a "pure" child struggling against an evil society that is trying to civilize him while he wants to remain a free spirit. Others believe that the main conflict of the novel is Huck against himself, struggling to figure out what he should do about Jim - turn him in, as society dictates, or hide him, as his conscience dictates. A third view is that the main conflict supersedes the characters and is a struggle between right and wrong or good and evil. Good arguments can be made to support all of these views as well as others. If you are writing about this, you need to decide for yourself what conflict you believe is the main one before you can decide which conflict or conflicts are secondary. What makes this novel so rich is that there is ample evidence within the narrative to support many differing views. I have had students write about this subject from totally different viewpoints and I have agreed with them all!

There is a lot of good information about this novel right here on enotes that can help you decide on what the conflicts are.

The climax of The Adventures of Huckleberry Finn involves a convoluted plan to secure Jim's freedom. After learning Jim is being held at the Phelps' house, Tom comes up with a plan to save him. He has Huck pose as Tom, and then Tom poses as his own brother, Sid. Huck suggests they find the keys to set Jim free, but Tom insists upon a plan involving journals, digging tunnels, and other far-fetched steps he's read in adventure novels.

When they finally get Jim out, Tom ends up getting shot by mistake. After being injured, he reveals that Jim was free all along: Jim's mistress, Miss Watson, set him free in her will. Now that she is dead, Jim is no longer anyone's slave.

The most humorous aspect of this is that Tom's plan is overly complicated and needless. Tom seeks to live out the escapist adventures he reads in novels, so he takes advantage of Jim's perilous situation for his own gratification. Twain is both parodying other adventure novels and exploiting Tom's own comedic flaws, namely his selfishness.

However, some might argue the true climax of the novel is when Huck decides not to tell Miss Watson where Jim is. He has been taught that there is nothing wrong with slavery and that keeping Jim from being rediscovered by his mistress is not only illegal but a sin.

When he tears up the letter sharing Jim's whereabouts to Miss Watson, claiming he's fine with "[going] to hell" to keep Jim free, Huck matures as a person. In many ways, that scene is the emotional climax of the story, because Huck finally comes into his own, rejecting a social rule that makes no sense to him anymore.