How did builders shift from the erection of one structure at a time to the mass construction of hundreds of thousands? "American Bridge" explores a radical reimagining, a new way of building that introduced uniformity and modularity on a global scale while enabling the connectivity essential to the rise of the nation-state. With tales of bygone infrastructure and astonishing images, Gregory Dreicer, our guest on the first episode of Season 6 of "Unfrozen" (also the first episode to feature two Gregs!) spans a deep gap in history. He tracks the transnational creative flows that propelled the development of beam, truss, and skeleton frame as industrial essentials, shaped by classical, capitalist, techno-utopian beliefs that still animate engineering and architecture.