Mary S. Clayton was born in Wayne County, Michigan, on January 19, 1857, the daughter of Joseph S. Clayton and his wife Mary. She had four siblings: Frederick, Cornelia, Margaret, and Elizabeth ("Libbie"). Clayton graduated from the Michigan State Normal School (now Eastern Michigan University) in 1877, with a focus in modern languages, and moved to Almont, Michigan, where she became a teacher at Union School. In the late summer of 1881, she married James F. Jordan, a native of Decatur, Michigan, who also graduated from the Michigan State Normal School in 1877. They lived in Lawton, Michigan, where he worked as a teacher, and eventually moved to Minneapolis, Minnesota, where he worked as a "credit man." They had at least five children: Lois, Anna, Robert James, Frances, and Veda.