The Fidèle, a ship sailing down the Mississippi River starting from St. Louis, on April Fools' Day, 1857
Fidèle means "faithful" in French, and that's both appropriate and ironic, because this ship is the scene of many interactions that test one's faith in others. The ship—like any ship of fools—is in some respects a microcosm of the world: it's got people from all over the place, and there's no escaping this mini-planet.
The Fidèle is sort of like a floating big city. It's got all the fancy excitement and all the risks, and it's a crowded place stuffed to the gills with passengers. These crowds are sometimes represented as having a single voice, like a Greek chorus, deriding the lone speaker in unison. At other moments, the crowd breaks apart, and we see a kaleidoscope of individuals. In this novel, we see both individual and collective.
The Fidèle is chugging along the Mississippi River, and the Mississippi River was kind of a big deal in the United States at the time this book made its debut. It was a major trade and travel route, and St. Louis was a bustling city with a reputation for crime.
Environment is important in this novel, and at times it even affects the characters' thoughts and opinions. If the title of Chapter 23 weren't enough ("In Which the Powerful Effect of Natural Scenery Is Evinced in the Case of the Missourian, Who, In View of the Region Round-About Cairo, Has a Return of His Chilly Fit"), then take a look, for example, at Pitch's dark thoughts as he looks upon Cairo: "He bethinks him that the man with the brass-plate was to land on this villainous bank, and for that cause, if no other, begins to suspect him" (23, 2).
Just a moment before, Pitch was chummy with the PIO man, but he's now extra dubious. He feels (realizes?) he's been bamboozled, and it was his surroundings that really brought him to this conclusion.
Finally, let's deal with the elephant in the room: this book totally takes place during April Fools' Day, and yes, April Fools' Day was a thing back then. This day is basically a free-for-all when practical jokes are all the rage. In this book, the characters aren't really pulling ha-ha-funny jokes on each other, but they sure are tricking and coning the bejezus out of each other.
And that's just how Melville likes it. He wants us to feel some of the absurdity of life that this novel just revels in.
Oh, and, um, by the way, this book was totally published on April 1, 1857…the same day it was set.
Maybe the joke's just on us, then?