We dedicate this third edition to Dr. Linda Olson Keller, DNP, RN, FAAN, whose vision and passion for public health nursing has inspired public health nurses worldwide to improve the health of populations. Her leadership led to the development of the Public Health Intervention Wheel, the Henry Street Consortium, and the Henry Street competencies. Her work has given public health nurses a confident voice in responding to the health needs of people where they grow, live, work, and play.