This narrative demonstrates how public and private power interacted during the post–World War II era to create America's unique health care system, a system based on a high-cost, corporate model financed and managed by insurance companies. The article compares the divergent political, organizational, and economic strategies of the American Medical Association (AMA), which represented physicians, and the Health Insurance Association of America (HIAA), which represented for-profit insurance firms. Even after the defeat of President Harry Truman's plan for a universal, government-managed system, policymakers in both parties attempted to reform the health care market, because most observers recognized that the embryonic insurance-company-funded model had inherent cost problems. In order to defeat numerous reform proposals, AMA and HIAA leaders allied to rapidly develop the market around insurance-company financing. Insurers and physicians constructed overlapping institutions to manage their increasingly close financial relationship, thus creating a pseudocorporate arrangement. In an attempt to control costs, insurance companies expanded their function beyond simply underwriting the risks associated with medical services consumption to also assuming a supervisory role, albeit distant, over health care delivery. When policymakers designed Medicare, they adopted the organizational framework that private health interests had already created, thereby legitimizing the previously contested high-cost model.