Twain is a somewhat naive man in his 20s when he begins the journey West with his brother. He is full of energy and enthusiasm to see the world, have adventures, and (he hopes) make his fortune. Twain never overthinks a venture. Instead he flies by the seat of his pants and takes risks that are sometimes foolish, sometimes downright dangerous. He has an unshakeable optimism that everything will turn out great, but when it doesn't, he shakes off every disaster and makes a fresh start on a new venture. Twain dreams of the good life and has a tendency toward laziness which he admits freely. And he never loses the opportunity to make fun of himself when the joke is worthy. Twain is a keen observer of everything around him, from people to landscapes, and uses language deftly to convey these observations to the reader. He also doesn't hesitate to speak his opinion or to skewer those people and institutions he finds ludicrous or disagreeable. Over the course of seven years, Twain travels across the West and all the way to Hawaii (the Sandwich Islands). As Twain's travels continue, he gains experience and a more mature perspective on life. After trying his hand at mining and reporting, he dreams up and implements a successful tour as a humorous lecturer. When Twain returns home to New York, he finds it isn't what it used to be. It has irrevocably changed, just as he himself has.
Twain's brother is never mentioned by name—it's Orion Clemens, for the record. Through him, Twain is able to make the trip West. Orion invites him to go along as his personal secretary, an opportunity Twain can't pass up. Orion shares the exciting overland journey and all its adventures with Twain and Bemis. Once in Nevada, Twain documents Orion's struggles managing the new territory, especially his difficulties in receiving funding from the federal government in Washington, D.C. Twain's brother is a conscientious, honest worker, doing the best work he can in a difficult position.
Mr. Ballou is an earnest, kind-hearted man who works as hard as the younger men and socializes easily with them. Ballou has a fondness for using large words he doesn't understand, but he does it with such ease that nobody ever questions his meaning. Unlike the younger men in the mining party, Ballou has more experience and more reasonable expectations about their prospects. Though he dreams of riches, too, he has a "wait and see" attitude that is both practical and usually accurate. It is Mr. Ballou who points out that Twain's first "strike" is not actually gold, but only mica—a glittering but worthless stone well-known to experienced miners. His words of wisdom, that not all that glitters is gold, stick with Twain for years. Ballou first finds a real silver prospect for the group, and he explains what the deposit's structure is like and how they will need to mine it, by digging a shaft or tunnel. Ballou also accompanies Twain to Esmeralda and survives the night in a snowstorm with him. (Although Ballou pledges to give up playing cards during this ordeal, it's a vow he doesn't keep.) Ballou eventually returns to Humboldt on his own, while Twain returns to Esmeralda.
Twain dedicates the book to Calvin H. Higbie, "an honest man, a genial comrade, and a steadfast friend." Higbie has decent knowledge of ore, as well as an instinct for finding it. Higbie and Twain try to track down Mr. Whiteman and his famous "cement mine" with no luck, so they travel together to Mono Lake. Higbie, strong and sensible, does most of the work (like rowing) and also solves problems of Twain's creation (such as retrieving the runaway boat). Back in Esmeralda, Higbie ingeniously discovers the "blind lead" that is worth millions. He dreams of building a big house in San Francisco and of traveling the world together with Twain, but the men lose through bad luck and negligence. In part, the loss is Higbie's fault, for instead of doing the work needed to secure the blind lead, he goes chasing off after Whiteman again instead. In the end, after nearly a decade of hard mining, Higbie uses the $2,500 he has managed to accrue to go into the fruit business.
A formidable man, Bemis carries an unreliable revolver and is a terrible shot with it. Bemis has a companionable relationship with the brothers, and together, they enjoy the adventure of the journey. At one point, Bemis is chased by a wounded buffalo during a hunt and he escapes up a tree. Afterward, he tells a whopper of a tall tale about the incident, claiming the bull climbed the tree and he hanged it with his lariat. Bemis later gets thoroughly drunk in Salt Lake City and falls asleep with his boots on.
The Mormons in Utah obey Young's directives as though they were the words of God himself. Anyone who speaks against Young may find themselves dead, possibly at the hand of his Destroying Angels, Mormon assassins. Twain notes that Young is a fair-minded leader, however. Young enforces a labor contract with Mormon workers who have walked off the job under contract to a local Gentile. Young admonishes the men for breaking their word, and they return to work without further objections. Twain quotes a lengthy speech supposedly made by Young as related to him by Mr. Johnson. Johnson, who once had breakfast with Young, said Young had so many children he couldn't remember their names. He had also complained of his many wives, and how if he bought one a present, he must buy the same for them all. The tale culminates with Young constructing a bed for his 72 wives to sleep in all at once.
Born in Illinois to good parents, Slade murders a man in his 20s and then flees to the West to escape punishment. Slade is both a cold-blooded killer who enjoys revenge and a devoted, loving husband who inspires the fierce loyalty of his wife. He is also a highly effective agent for the stagecoach company who brings order to his route with an iron fist, not hesitating to kill troublemakers and bandits. Twain dines with Slade during a stagecoach stop, an occasion that both thrills him and makes him incredibly nervous. Slade is later hanged in Montana for being a dangerous public nuisance for shooting up businesses while drunk and for defying a local group of vigilantes. At his hanging, he pleads and cries for his wife, prompting some to call him a coward. Twain, however, cannot see how such a proven fearless man could ever be thought a coward.