what is the history of the carnival people?

This is how all of the carnival members began - as people who couldn't accept the natural unhappiness of life, and so took on the greater unhappiness of defying fate.

Tom Fury is the lighting rod salesman in the first chapter. He gives the boys a complimentary lightning rod because he worries for their safety. He also makes a brief appearance later in the novel, just before the carnival comes to town. Later, he reappears as The Dwarf, an insane being apparently transformed by carnival for some transgression, though the exact reason for his change is not clear.

Mr. Dark - along with Mr. Cooger - is the proprietor of the carnival. He has been alive for an untold number of years, leading carnivals across the country. He rides the carousel to stay young. His carnival feeds off of the fears and desires of others, and as the leader of the carnival, Mr. Dark can be imagined to do the same. His body is covered in tattoos that writhe and dance as he flexes his muscles; therefore he is also known as the Illustrated Man. When the boys learn the evil secret of the carnival, he hunts and kidnaps them. In the climax of the novel, he makes himself younger on the carousel and approaches Charles as a boy. When Charles discovers this deceit, he hugs the now-young Mr. Dark, "starving" him of the fear and desires that he needs to survive, and thus killing him.