Chiropractic is a system of healing that holds that disease results from a lack of normal nervous function caused by a disordered relationship between the musculoskeletal and nervous systems. The American Medical Association organized in the early 1900s and developed into a powerful force, influencing nearly every aspect of the U.S. health care system. A close examination of chiropractic history helps identify the limits and the forces that define them. Chiropractic was a natural system of healing that allowed the body to manifest its intrinsic restorative powers. A milestone in the evolution of chiropractic was an increasing acceptance of the germ theory of disease. The 1950s and 1960s were a golden age for medicine. Federal support for biomedical science expanded enormously after World War II, and impressive diagnostic and therapeutic advances aided medicine's emergence as the most highly regarded profession in the United States. Chiropractic achieved federal recognition when it became incorporated into the Medicare and Medicaid programs.