This collaborative project proposes a new historical framework for understanding the modern world as shaped by what we term the “Infrastructure Age.” Since the 1870s, the expansion of large-scale infrastructural systems—for transport, energy, water, communications, finance, social provision, and more—has reorganized social, political, economic, and ecological life. These systems expanded state and corporate power and redefined citizenship expectations, even as they intensified ecological crises from climate change to freshwater scarcity. We plan to bring together Chicago-based and Paris-based historians with diverse regional and sectoral expertise to study the century-long evolution of the Infrastructure Age comparatively across the global North and South, from its late nineteenth-century consolidation through the crises of the 1970s and the subsequent neoliberal turn. The collaboration will culminate in a collectively authored volume which aims to develop new conceptual and methodological tools for the historical analysis of infrastructure. The project thereby aims to reposition infrastructure as a frontier for historical inquiry and to contribute to broader debates on sustainability, decarbonization, and inclusive social futures.