Charlotte is a resilient orphan growing up at a New Hampshire work farm. As the only girl among the children, she is expected to labor in the kitchen but vastly prefers working in the stables. She possesses an exceptional, natural talent for riding and calming horses. Frustrated by the strict gender expectations that keep her indoors, she dreams of a free life where she can work with the animals she loves.

Vern is the stable master at the orphanage and a former slave who escaped the South to find freedom. He is a quiet, patient man who treats the animals with profound respect, believing every horse deserves a dignified name that tells a story. He serves as the primary nurturing adult in Charlotte's early life, providing her with guidance and a refuge from the kitchen.

Hayward is a young orphan with red hair and prominent ears who forms a deep bond with Charlotte. Two years her junior, he relies on her protection from bullies while offering her steadfast loyalty in return. He spends his time daydreaming with Charlotte about leaving the facility to start their own private horse ranch.

Mr. Millshark is the short, mean-spirited overseer of the New Hampshire orphanage. He operates the facility more like a work farm, exploiting the children for unpaid labor while presenting a charitable image to the town. He actively suppresses Charlotte's interest in horses, insisting she behave in a lady-like manner.

Ebeneezer is a bald, practical man who owns a horse stable and stagecoach business in Massachusetts. He struggles to find reliable stable hands until he discovers a young worker secretly cleaning his stalls at night. He values hard work and natural ability, judging people by their skill with horses rather than their background.

Mrs. Boyle is the cook at the orphanage and the main female authority figure in Charlotte's daily life. She views Charlotte strictly as a servant and actively hides her from prospective adoptive parents to retain her free kitchen labor. She represents the confined, domestic existence that Charlotte actively rejects.

William is an older orphan boy living at the same facility as Charlotte and Hayward. He resents Charlotte's presence in the stables and harbors deep jealousy over her superior riding abilities. He frequently targets younger or weaker children to make himself feel powerful.

Margaret is a hardworking widow living on a modest plot of land. She supports herself by selling eggs in town but faces the constant threat of bank foreclosure on her home. She demonstrates quiet resilience as she tries to maintain her independence despite severe economic limitations.

James is an ambitious former stable boy who leaves the East Coast to seek his fortune during the California Gold Rush. Recognizing the high demand for transportation in the booming western territories, he helps establish a new stagecoach line and seeks out the best drivers to join his enterprise.

Frank is an opportunistic former stable worker who ventures to California alongside James Birch. He helps establish the California Stage Company to capitalize on the rapid population growth and the massive need for reliable stagecoach routes between the gold mines and Sacramento.