In Chapter 20, the King and the Duke go to swindle people at a religious revival called a "camp meeting."
There were a lot of people there -- maybe a thousand. They were listening to preaching going on in big sheds. There were vendors selling things like watermelon and lemonade.
As the preacher would preach, the people would all scream and shout. The preacher would call people up to be saved by Jesus and the audience would scream and shout some more.
Then the King goes and claims he used to be a pirate before he got saved by Jesus. By doing this, he gets people to give him money so he can go help save the other pirates. He gets over $85 this way.
The camp meeting is a large rural community gathering that functions literally as a “sideshow” of human behavior for Huck and Jim. Like a country fair, music festival, or church service, the camp meeting allows the community to gather and watch performances, eat special foods, and even partake in courtship rituals.
The text emphasizes the poverty and simple clothing of the attendees as well as the makeshift qualities of the shelters and furniture. A preacher is leading a large group of people in a “call and response” song that affects the people deeply, and they begin to respond with their bodies. When the preacher begins his sermon, he conjures a serpent in the wilderness and calls the poor and suffering to heaven, and the people respond even more, falling to the ground, weeping, and gesturing. The king and duke witness these behaviors and see the people as ripe for the plucking.
The preacher’s sermon leads to the central event of the camp meeting: the king’s performance where he tells a tall tale of pirating and transformation. Captivated by his tale, the rural people take up a collection for the king and he earns a large sum of cash. Ironically, the preacher’s warning about the serpent and call to the people’s salvation has led them to be exploited by the king, driving them further into poverty.
The camp meeting draws an ironic contrast between the power of organized religion and the power of nature. On the previous night, Huck spent the night on the river in a terrific storm where he witnesses the power of nature at its finest. Huck is unprotected by clothing or shelter during the storm, yet he emerges unharmed and in awe of its power. In contrast, the religious performance at the camp meeting causes the people to fall further into a state of ignorance and deprivation.