With President Obama’s health care reform currently under intense partisan scrutiny in the United States, this article is an objective resource for understanding the ways in which Medicare has historically served as a weather vane for charting the changes to the American health care system. During its nearly fifty-year tenure as the standard for the provision of medical care in the U.S., Medicare has evolved in fits and spurts, with its core structure shifting over time as the result of each decade’s economic and political climate. It is only by understanding these past revisions, both independently and in the context of the concurrent changes in other nations around the world, that we can fully comprehend the state of America’s health care...