In the early decades of the 19th century, physicians in the USA enjoyed unquestioned authority in medicine and increasing state recognition. But by mid-century, their monopoly had given way to a raucous free market for medical care. To explain the causes and consequences of this dismantling of a professional monopoly, we draw on political sociology. We argue that to maintain a monopoly, a dominant profession must defend its cultural authority against rival claims and preserve its institutional support from the state. A dominant profession can lose its monopoly if rival occupations mobilize to challenge its cultural authority and if populist political coalitions mobilize to repeal laws upholding professional monopolies. Our analysis, which covers all states in the Union by 1860, reveals that the dynamics of contention, both within the system of professions and in the wider political arena, can erode the foundations of professional monopolies.