Ann Seton was born in New York, New York, and died in Old Greenwich, Connecticut. She was the daughter of English-born naturalist and pioneer of the Boy Scouts of America, Ernest Thompson Seton and Grace Gallatin Seton. She is interred at Putnam Cemetery in Greenwich.

Her historical novels were noted for how extensively she researched the historical facts, and some of them were best-sellers: Dragonwyck (1944) and Foxfire (1950) were both made into Hollywood films. Three of her books are classics in their genre and continue in their popularity to the present: Katherine, the story of Katherine Swynford, the mistress and eventual wife of John of Gaunt, and their children, who were the direct ancestors of the Tudors, Stuarts, and the modern British royal family; Green Darkness, the story of a modern couple plagued by their past life incarnations; and The Winthrop Woman about the notorious Elizabeth Fones, niece and daughter-in-law of John Winthrop, the first governor of the Massachusetts Bay Colony. Most of her novels have been recently republished, several with forewords by Philippa Gregory.

Her novel Devil Water concerns James, the luckless Earl of Derwentwater and his involvement with the Jacobite rising of 1715. She also narrates the story of his brother Charles, beheaded after the 1745 rebellion, the last man to die for the cause. The action of the novel moves back and forth between Northumberland, Tyneside, London, and America.

Seton stated that the book developed out of her love for Northumberland. Anya certainly visited her Snowdon cousins at Felton. Billy Pigg, the celebrated Northumbrian piper played "Derwentwater's Farewell" especially for her. The novel shows her typical thorough research of events and places, though the accents are a little wayward. Seton said that her greatest debt of all was to Miss Amy Flagg of Westoe Village in South Shields, her father's birthplace.