Petry was trained as a pharmacist before she turned to literature. In addition to Harriet Tubman, she became known for several other juvenile books and, more widely, for four novels. The novels earned her acclaim, and her writing generally has been praised for its simplicity and control.

When Harriet Tubman appeared in 1955, the critical response to it was almost unanimously laudatory. Reviewers praised the skill, warmth, and sensitivity of the biography. Library Journal noted Petry’s effective treatment of Tubman’s childhood and the early influences that led to her later work. The Saturday Review argued that Petry’s book demonstrated careful research and great narrative economy. Both those reviewers considered Harriet Tubman to be an advance in the available literature on the subject, and the Chicago Sunday Tribune explicitly placed Petry’s book in favorable comparison with such other Tubman biographies as Dorothy Sterling’s Freedom Train: The Story of Harriet Tubman (1954) and Anne Parrish’s A Clouded Star (1948). Booklist and The New Yorker both commented on the evocative power of Petry’s book and recommended it as an addition to any library for young readers.