First published in 1938, Penn quickly established itself as a cornerstone in juvenile and young adult literature, evidenced by its nine reprintings over the subsequent twenty-four years. Its acclaim was cemented when it was named a 1939 Newbery Medal Honor Book. The text's sophistication and ability to effectively dramatize historical narratives are highlighted in Children and Books (1947) by Zena Sutherland and May Hill Arbuthnot. These commendations underscore Penn's status as a classic in young adult biography. The book's author, Vining, has received numerous honorary degrees in recognition of her significant contributions to literature.

A major element contributing to the book's enduring popularity among young adults is its portrayal of Penn as an immensely likable figure. Characterized by his forthrightness, truthfulness, and generosity, Penn emerges as a person many would aspire to have as a friend. His wit, modesty, and ability to support those in trouble add layers to his appeal. Despite his serious nature, he possessed a remarkable ability to laugh at himself. Penn was unique in his steadfast adherence to principles, balancing humanity, justice, and geniality. A committed freedom fighter, he fiercely advocated for nonviolence and exuded an infectious vitality and magnetism.

Penn's enduring legacy lies in his foundational role in establishing the principles of religious and political freedom which later became hallmarks of the United States. The book Penn aptly serves as a tribute to his remarkable life and the ideals he championed.