The famous St. Louis World’s Fair of 1904 was a vast celebration of the new century and its promise of a future governed by technological and scientific progress. It is not often remembered that in the heart of this paean to modernity stood an enormous and astonishingly life-like replica of the Old City of Jerusalem. Evoking the past rather than the future and transcendence rather than materiality, what was Jerusalem doing in the St. Louis Fair? How did its presence challenge, complicate, or legitimize the popular narratives of modernization with which it was surrounded? Through a description of the fair and the replica—and contra theories that continue to adhere to the secularization thesis and its structuring binaries—this essay is an examination of the preservation and deployment of religious themes and symbols within modernity.