At the end of the 5th century BC, a prosperous, imperial, and democratic city-state (polis) embarked on a long and demanding war. The conflict severely strained Athens’ resources, compromised its commitment to democracy, and ultimately plunged the city into civil war. In its aftermath, Athens was again a democracy, and the city moved fast to restore her position as the highest performing polis in the prosperous Greek world. This dissertation investigates the institutional roots of democratic consolidation and economic resilience in the aftermath of war. It argues that, to overcome the threats of internal violence and limited resources, the Athenians established a new, self-enforcing constitution. The new constitutional order enabled the polis to harness the economic potential of available resources and actors—thus maximizing economic efficiency—without loss of political stability in the form of devolution into protracted civil war and without elite capture. In particular, the constitution fostered stability and growth by creating an inclusive legal order capable of providing a) broad institutional access to political as well as economic actors, and b) coordination between centralized and decentralized law enforcement institutions, which allowed for the effective policing of wrongdoing and the fair distribution of public goods. Moving from North, Wallis and Weingast’s (2009) theory of development as the transition from ‘natural state’ to ‘open access order,’ this dissertation suggests that ancient Athens was developed in many relevant respects, and that the history of Athens’ development may offer important insights for rethinking the process and the goals of institution building in the developing world.