Health care reaches more children under age three in the United States than any other family-facing system and represents the most common entry point for developmental assessment of and services for children. In this article, Adam Schickedanz and Neal Halfon examine how well the child health care system promotes healthy child development early in life. They also review children's access to health care through insurance coverage, the health care system's evolution in response to scientific and technical advances, and the shifting epidemiology of health and developmental risk. The authors find that the health care system is significantly underperforming because it is constrained by antiquated conventions, insufficient resources, and outmoded incentive structures inherent in the traditional medical model that still dominates pediatric care. These structural barriers, organization challenges, and financial constraints limit the system's ability to adequately recognize, respond to, and, most importantly, prevent adverse developmental outcomes at the population level. To achieve population-level progress in healthy child development, Schickedanz and Halfon argue that pediatric care will need to transform itself and go beyond simply instituting incremental clinical process improvement. This will require taking advantage of opportunities to deliver coordinated services that bridge sectors and focusing not only on reducing developmental risk and responding to established developmental disability but also on optimizing healthy child development before developmental vulnerabilities arise. New imperatives for improved population health, along with the growing recognition among policy makers and practitioners of the social and developmental determinants of health, have driven recent innovations in care models, service coordination, and coverage designs. Yet the available resources and infrastructure are static or shrinking, crowded out by rising overall health care costs and other policy priorities. The authors conclude that child health systems are at a crossroads of conflicting priorities and incentives, and they explore how the health system might successfully respond to this impasse.