Mary was born Mary Elizabeth Mapes to Prof. James Jay Mapes and Sophia Furman in New York City. She acquired a good education under private tutors. In 1851 she married the lawyer William Dodge. Within the next four years she gave birth to two sons, James and Harrington. In 1857, William faced serious financial difficulties and left his family in 1858. A month after his disappearance his body was found dead from an apparent drowning, and Mary Mapes Dodge became a widow.
In 1859 she began writing and editing, working with her father to publish two magazines, the Working Farmer and the United States Journal. Within a few years she had great success with a collection of short stories, The Irvington Stories (1864), and a novel was solicited. Dodge then wrote Hans Brinker, or the Silver Skates, which became an instant bestseller.
Later in life she was an associate editor of Hearth and Home, edited by Harriet Beecher Stowe. She had charge of the household and children's departments of that paper for many years. She became an editor in her own right with the children's St. Nicholas Magazine, for she was able to solicit stories from a number of well-known writers including Mark Twain, Louisa May Alcott, and Robert Louis Stevenson. St. Nicholas became one of the most successful magazines for children during the second half of the nineteenth century, with a circulation of almost 70,000 children.
Dodge died at her summer cottage in Tannersville, New York, in 1905. She is buried in the Evergreen Cemetery, at 1137 North Broad Street, Hillside, New Jersey.