Rachel McMasters Miller married Roy on June 11, 1913. The daughter of Mortimer Craig Miller and Rachel Hughey McMasters, she was born on June 30, 1882 in Turtle Creek, Pennsylvania and was educated at the Thurston School in Pittsburgh and Miss Mittleberger's School for Girls in Cleveland. She and Roy had four sons: Alfred Mortimer Hunt (1919-1984), Torrence Miller Hunt (1921-2004), Roy Arthur Hunt, Jr. (1924-1981), and Richard McMasters Hunt (1926-).

Throughout her life, Rachel maintained an active interest in botany, horticulture, and bookbinding. An accomplished bookbinder, she exhibited thirty-four of her books at the New York School of Applied Design for Women in 1911, an exhibit that later moved to the Wunderly Galleries in Pittsburgh. Her first gift to Roy was a copy of The Book of Common Prayer, which she had bound and appropriately tooled in aluminum.

Rachel was a member of more than thirty horticultural and botanical organizations, some of which she helped to establish. In 1956, she was named Honorary Vice President of the American Horticultural Society. She authored books and papers, and lectured widely in the fields of horticulture and literature. Carnegie Institute of Technology awarded her an honorary degree of Doctor of Humane Letters in 1960.

Due to her love of books and flowers, Rachel acquired a remarkable collection of historically significant botanical books and art. In 1961, she and Roy established the Hunt Botanical Library at Carnegie Institute of Technology (now the Hunt Institute for Botanical Documentation at Carnegie Mellon University). The Institute continues its curatorial work and research in systematic botany and serves as a resource for botanists from around the world.