This article examines the history and formation of Medicare and Medicaid to determine how America’s two major public health insurance programs came to have such vastly different implementation structures. Drawing upon theories of social construction and path dependence, findings show how the programs were set on divergent paths. This article also explores how the intergovernmental nature of Medicaid has promoted inequities, both between programs and among recipients across states. The findings show how social construction can influence the policy tool chosen and how the implementation structure impacts the individuals whom these programs are intended to serve for years to come.