As the United States industrialized, its state constitutions began to include protections for laborers. In this article, I describe the origins of these constitutional provisions and ask why labor organizations and other reformers pursued their inclusion in state constitutions. I argue that they saw state constitutions as a vehicle to prompt reluctant legislatures to pass protective statutes, to entrench existing protections against future legislatures, to safeguard labor legislation from constitutional challenges in state courts, and to facilitate further union organizing. Labor activism in this arena is particularly interesting in light of the literature on constitutional change, which contends that constitutional development is a tool through which actors attempt to usher courts into political conflicts; in contrast, I will argue that unions turned to constitutional change in large part to exclude courts from policymaking. Further, the union activism on behalf of constitutional change serves as a challenge to the prominent view among many scholars of American political development and law that judicial hostility to worker rights and union organizing discouraged unions from demanding state protection or institutionalizing their demands through law.