With her indomitable will, limitless energy, and sense of mission, Clara Barton was ideally suited to work on the battlefront during the Civil War and in disaster relief as the head of the American Red Cross, whose founding was largely a personal achievement. Born on Christmas Day 1821 to prosperous farmers Stephen Barton and Sarah Stone Barton in Oxford, Massachusetts, Clarissa Harlowe Barton was a shy and sensitive child with a quick temper. Born ten years later than her youngest sibling, Clara grew up with no playmates but with a good education. Her mother, troubled by Clara's shyness, consulted phrenologist Lorenzo Fowler, who offered the advice, "Throw responsibility upon her. . . . As soon as her age will permit, give her a school to teach." So, at age fifteen, Clara Barton began a career as a teacher.

Teacher.

Despite her youth and inexperience, she was immediately successful and...