Caddie is an eleven-year-old tomboy living on a farm in western Wisconsin during the 1860s. Following the death of her sister Mary, her father gave her permission to run wild with her brothers to build her health. She strongly prefers outdoor adventures, hunting, and repairing clocks over the ladylike expectations of her mother and society. She is competitive, fiercely loyal to her family, and approaches the world with natural curiosity and empathy.

Tom is Caddie's older brother by two years and her primary partner in adventure. He acts as a leader during their excursions into the woods and is fiercely protective of his siblings. Though he appreciates his tomboy sister and shares her love for the Wisconsin frontier, he also harbors a quiet admiration for girls who display more traditionally ladylike traits.

Mr. Woodlawn is the patriarch of the family, an Englishman who works his farm and serves as a master mechanic at the local mill. Having grown up in poverty after his father was disowned by aristocratic relatives for marrying a shoemaker's daughter, he places immense value on hard work, equality, and self-reliance. He actively encourages Caddie's independence and teaches her clock repair.

Mrs. Woodlawn is Caddie's mother, a woman who originally hails from Boston and frequently finds the Wisconsin frontier lacking in civilization. She desperately wishes Caddie would adopt more refined, ladylike behaviors, though she tolerates her daughter's wildness out of respect for her husband's wishes. She works hard on the farm, raising turkeys and managing a large household.

Indian John is a local Native American who maintains a friendly, trusting relationship with the Woodlawn family. He is known to be kind, having taken a special interest in Caddie's red hair when she was younger. He stands as a peaceful figure amidst the growing fear and tension among the white settlers.

Warren is Caddie's younger brother by two years. He happily joins Tom and Caddie on most of their exploits, often mimicking their ideas and relying on their leadership. He is devoted to his older siblings and shares their enthusiasm for the outdoors, though he struggles with public speaking and school presentations.

Hetty is Caddie's younger sister, known as the self-appointed newsbearer and tattletale of the family. Her habit of spying and telling on her older siblings stems from a deep loneliness and a desire to be included in their tight-knit group. She slowly learns to establish her own identity and bridge the gap with her sister.

Clara is the oldest of the Woodlawn children and the only one who retains memories of their life in Boston. She aligns closely with her mother's refined sensibilities and serves as a traditional, ladylike contrast to Caddie's wilder disposition.

Edmund is Mrs. Woodlawn's brother, an unpredictable visitor who brings chaos, practical jokes, and a love for hunting to the farm. He has a complicated dynamic with Caddie, marked by playful challenges that sometimes cross the line into irresponsibility.

Annabelle is the Woodlawns' polished cousin from Boston. Reared as a proper lady, she initially appears delicate and fixated on city superiority, making her a prime target for her rustic cousins' practical jokes.

Obediah is a rough, crude teenager who challenges the teacher's authority. He initially serves as a schoolyard bully, prompting Caddie and her brothers to stand up to him, though circumstances later reveal a more capable side to his character.

Miss Parker is the local schoolteacher who must maintain order among a diverse and sometimes rowdy group of frontier children. She is strict but ultimately fair in her administration of discipline and education.

Katie is the local seamstress's daughter, a quiet, polite, and traditionally ladylike girl who is easily frightened by frontier life and Native Americans. She attracts the quiet affection of Tom Woodlawn.

Mr. Tanner is the circuit rider, a traveling preacher who covers western Wisconsin. He enjoys reminiscing about Boston with the Woodlawns and relies on Mr. Woodlawn to fix the broken clocks he collects during his travels.

Sam is a white settler who yields to social pressure and prejudice. He grows ashamed of his Native American wife as more white people move to the frontier, ultimately altering the structure of his family.

Mrs. Hankinson is a Native American woman married to a white settler. As more white settlers arrive in the area, she faces increasing prejudice and pressure regarding her place in the community, leading to a heartbreaking separation from her children.