Dramatic forces evolving in the late 19th century contributed to the transformation of the clinical care of individuals with cancer. The building of cancer hospitals, reporting of increasing numbers of cancer cases, medical specialization, and the declared war on cancer contributed significantly to the progress of change. Physician acknowledgment of the growing impact of cancer resulted in the formation of the American Society for the Control of Cancer in 1913. The clinical work of nurses was essential yet overlooked in many historical accounts of the time. Historical research provides evidence of the development of the oncology nursing specialization in the 1900s through the 1940s. Nurses required knowledge, skills, compassion, and fortitude to provide care to individuals with advanced cancers undergoing radical and sometimes dangerous therapies in hospitals and homes. Early nursing leaders provided the vision, established the foundation, and cultivated the passion for the emergence of the specialty.