Many of Rylant's books are about her childhood in Appalachia, her pets, the joys and hardships of family life, and the feelings of loners. Many of her books are written in series.
Rylant was born in Hopewell, West Virginia, the daughter of a U.S. Army veteran, John Tune Smith, and Leatrel Smith née Rylant. Rylant uses her mother's maiden name as her pen name. She spent her first four years in Illinois. Her parents separated when she was four years old, and she was sent to live with her mother's parents in Cool Ridge, West Virginia, while her mother attended nursing school and was able to visit her only a few times a year. Growing up in the Appalachian region of the U.S. during the 1960s, Rylant lived in a very depressed economic environment. Her grandparents, extended family and kind local townspeople provided a loving, nurturing, safe environment, while the little girl "waited ... until someone could return for me", but they were very poor and lived a rustic life, with no electricity, running water or automobile. As a result, she never saw children's books as a child, reading mainly comic books and enjoying the outdoors.
Four years later, she moved back with her mother, who had relocated to nearby Beaver, West Virginia.There had been no libraries or bookstores in Cool Ridge, and there were none in Beaver. Rylant never saw her father again, and he died when she was thirteen years old. She later wrote, "I did not have a chance to know him or to say goodbye to him, and that is all the loss I needed to become a writer." When she was nine years old, Rylant fell in love with Paul McCartney and The Beatles. However, her West Virginia childhood was the major influence on her works, and many of them deal with life in the Appalachian region. As a teenager, Rylant became enchanted with Robert Kennedy, whom she met during his presidential campaign. She was deeply affected by his assassination. Also important to her emotional development was her relationship with a boy from school.
Rylant earned a B.A. degree from Morris Harvey College (now the University of Charleston) in 1975 and a M.A. degree from Marshall University in 1976, discovering and studying English literature and greatly enjoying her years in school. In 1977, she married Kevin Dolin. Unable to find a job in her field after completing college, she first worked as a waitress and later as a librarian at the Cabell County Public Library in Huntington, West Virginia, where she finally became acquainted with children's books. She taught English part-time at Marshall University in 1979 and wrote her first book, When I Was Young in the Mountains, based on her experiences as a young child living in the country with her grandparents. The picture book, which Rylant later said took her an hour to complete, earned an American Book Award in 1982 and was a Caldecott Honor Book. Her marriage with Dolin ended in 1980, and she earned a Masters degree in Library Science from Kent State University in 1981. She lived in Kent, Ohio, for many years, working as a librarian at the Cincinnati Public Library. She later moved to Akron, Ohio, and worked at the Akron Public Library while teaching English part-time at the University of Akron. During the early 1980s, she was married briefly to a professor at the University of Akron.
Rylant followed her inaugural effort with six more picture books based on her childhood experiences. Her 1983 book, Miss Maggie, deals with themes of aging. Her first poetry collection, Waiting to Waltz: A Childhood (1984), was also autobiographical, based on both happy and sad events or on people she knew, drawing universal emotions from the incisive portraits. Rylant became interested in writing poetry when she read some poetry in college by David Huddle. She said of his Paper Boy, that the strong characters were "People whose lives are hard but are proud of who and what they are." In 1985, Rylant decided to write full-time. Her first novel, A Blue-eyed Daisy (1985), describes a year in the life of a young girl, including such events as her first kiss and the funeral of a classmate, and her relationship with her father, who, like Rylant's real-life grandfather, is injured in an accident and loses his job. Her 1986 book, The Relatives Came, describes how she slept on the floor when company visited. The same year, she published one of her most well-received books, A Fine White Dust. This young adult novel portrays a boy who becomes a disciple to a charismatic preacher, leaving his parents and friends. When the preacher runs off with a young woman, the boy, despite his feelings of betrayal, strengthens his faith in God and discovers a more realistic view of human nature. The book was named a Newbery Honor book.
In 1987, Rylant published the first of her popular Henry and Mudge series books, Henry and Mudge: The First Book of Their Adventures. In this book for beginning readers, Henry, an only child, forms a deep attachment with a puppy who grows to be an enormous drooling dog, Mudge. When Mudge is lost, Henry is despondent, and when he is recovered, the two are overjoyed. Since then, she has published dozens more Henry and Mudge books, as well as picture books, books for older readers, including young adult novels and story collections, and collections of poetry. Her critically praised 2004 picture book, Long Night Moon, describes the different moons that Native American cultures use to mark the changing seasons. 1995's The Van Gogh Cafe is one of the author's favorites. Her books often deal with the joys and hardships of family life, with animals and the outdoors, especially in the Appalachian region, and her characters are often loners or people facing hardships. Her 1991 non-fiction picture book for older readers, Appalachia; The Voices of Sleeping Birds, is a vivid picture of life in Appalachia and the warmth of its people.
Rylant's 1992 young adult novel, Missing May, is a touching story about a girl who lives with relatives after the death of her mother and who must comfort her uncle after the death of his beloved wife. Beginning in the early 1990s, Rylant has published several series designed for younger readers, including the Lighthouse Family, High-rise Private Eyes, and Everyday Books series, the last of which is a series for very young children that she illustrated herself. She also illustrated several of her other books, including the playful Dog Heaven (1995), about an ideal dog afterlife. Other poetry collections have been God Went to Beauty School (2003) and Boris (2005). In 1993, Rylant relocated to Eugene, Oregon, with her son Nathaniel from her first marriage. In 2003, she moved to Portland, Oregon.
Rylant has received a number of awards and honors for her work. A Fine White Dust (1987) won a Newbery Honor, and Missing May (1993) won a Newbery Medal. When I Was Young in the Mountains (1982) and The Relatives Came (1985) received Caldecott Honors. The Relatives Came and Appalachia: The Voices of Sleeping Birds (1991) are each Boston Globe/Horn Book Honor Books, as is Missing May, which deals with the loss of a loved one. A Kindness (1988), Soda Jerk (1990), and A Couple of Kooks and Other Stories about Love (1990) have each been named a "Best Book of the Year for Young Adults" by the American Library Association.