This article investigates the history of the formation of the red-light district of Tehran in 1922, to tackle larger questions about the genealogy of the constitutional Islamic state in Iran in the twentieth century. Through an engagement with the Islamic local campaign against prostitution and the state's subsequent sovereign decision to form the district, this article demonstrates how Islamic public sensibilities moved to the forefront of analytics of governance, under postconstitutional state formations (1911–). This revisionist narrative remaps the force of religion in Tehran, a city that is so often glossed as a case of state-oriented top-down secularization and subsequent Islamization in the twentieth century. The aim is not to question the process of secularization or to render it incomplete, but to demonstrate how secularism in Iran negotiated and consolidated a particular relationship between Islam and sovereign modern rule. As such, this work reads the history of the district against the grain of the grand narrative of the Islamic Revolution's (1979) moment of rupture to trace the genealogical roots of moral governance in the Islamic Republic today, within the postconstitutional state formations in the early twentieth century.