This paper provides a historical analysis of the changing significance of the most influential statement ever made on inequality and development—Simon Kuznets’s “inverted U-curve hypothesis.” The shifting interpretations and appropriations of the hypothesis over time—from its status as a speculative supposition in 1955, to its rise and fall as a reified socioeconomic law, to its contested standing in the social sciences today—demonstrate how Kuznets’s arguments, originally advanced under more limited conditions, became transformed into overarching theoretical, empirical, and political constructions. This history suggests that even empirically grounded and testable social science models are contingent on the broader social and political contexts in which they are produced and negotiated.