Power struggles between debtors and creditors about unpaid debts have animated the history of economic transformation from the emergence of capitalist relations to the recent global financial crashes. Illuminating how ordinary people fought for economic justice in Mexico from the eve of independence to the early 2000s, this study argues that conflicts over small-scale debts were a stress test for an emerging economic order that took shape against a backdrop of enormous political and social change. Drawing on nearly 1,500 debt conflicts unearthed from Mexican archives, Louise E. Walker explores rapidly changing ideas and practices about property rights, contract law, and economic information. This combination of richly detailed archival research, with big historical and theoretical interpretations, raises provocative new questions about the moral economy of the credit relationship and the shifting line between exploitation and opportunity in the world of everyday exchange.