Over the past 50 years, health care has been making a growing contribution to population health in many countries. Yet its benefits are still denied to many people worldwide. This article describes how many countries, both developed and developing, have pursued the quest to achieve universal health care. This has been an explicitly political process. In Europe, it emerged from a belief in solidarity, a fear of revolution, and a changing view of the role of the state. In developing countries, progress was more erratic, characterized by debates about the affordability of universal health care, until it was realized that functioning health systems were essential to deliver development goals. Throughout, the United States has been an exception. An analysis of progress toward universal health care, combining a review of existing theories and new empirical analysis, identifies five factors as important: the strength of organized labor and left-wing parties, adequate economic resources, absence of societal divisions, weakness of institutions that might oppose it (such as organized medicine), and windows of opportunity. Having noted the substantial benefits accruing from universal health care, the article concludes with an analysis of how universal health care is under threat in some European countries and a warning about the risks posed by current radical austerity policies.