Jack is a twelve-year-old orphan who leaves his comfortable life in Boston to join the gold rush. He wants to save his aunt's estate from bankruptcy by striking it rich in the West. Though young and small for his age, he works hard to prove his toughness on the frontier. He drinks bitter coffee and climbs ship rigging to test his bravery.

Praiseworthy is a highly trained English butler who manages the Flagg family household. He accompanies Jack on the dangerous journey west out of deep devotion to Arabella. He initially relies on his formal attire and strict manners to handle life at sea. As the journey progresses, he applies his meticulous organizational skills to frontier challenges.

Cut-Eye is an opportunist and thief heading to the goldfields. He uses false identities to steal from his fellow travelers. He points to a facial scar as evidence of a wealthy dueling background. He constantly looks for weaknesses in the people around him.

Arabella is Jack's young, unmarried aunt. She took her nephew and nieces into her Boston mansion after their parents died of cholera. She faces severe financial difficulties that threaten her home. Her gentle nature inspires deep loyalty from her household staff.

The rough commander of the Lady Wilma ship. His crew refers to him as the "wild bull of the seas" because of his fearsome temper. He is obsessed with beating a rival ship to earn a new command. He balances ruthless sailing tactics with moments of fairness toward his passengers.

Constance is Jack's younger sister. She lives in the Boston mansion under Arabella's care after the death of their parents.

Sarah is the youngest of the Flagg siblings. She remains in Boston with her aunt while her brother travels west.

Good Luck is a small black pig kept as part of the ship's livestock. Jack quickly befriends the animal and tries to protect it from becoming the crew's dinner.

Dr. Buckbee is a horse doctor traveling with a wooden leg. He carries a treasure map that supposedly reveals a rich gold deposit. He blows a loud horn to guard his belongings while sleeping.

A large, physically imposing man traveling on the Lady Wilma. He tracks the weather and alerts the cabin when the ship finally reaches the Pacific Ocean.

A Yankee trader who invests his entire fortune into eighteen barrels of potatoes. He plans to sell them in San Francisco but panics when they begin to spoil in the heat.

A French passenger transporting valuable grape clippings to California. He has money but lacks the fresh water necessary to keep his plants alive during the hot sea voyage.

Quartz is a rugged miner who recently arrived from the goldfields. He desperately wants a haircut before meeting his arriving fiancée. He teaches the newcomers how to pan for gold using his own shorn hair.

A scruffy, quick-tempered prospector working a claim in Hangtown. After realizing his mistake with the wash pan, he apologizes by teaching Jack and Praiseworthy the rules of mining law and sharing his terrible camp coffee.

An auctioneer in the mining camp who sells miscellaneous goods. He auctions off a mistakenly shipped bushel of neckties to an embarrassed Jack.

An enormously strong, illiterate brawler with a massive chest and thick neck. He hears rumors of Praiseworthy's fighting skills and demands a bare-knuckle boxing match to prove his dominance.