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February 14, 1905. A stick of dynamite detonates under the Hudson River — and the ground above swallows a locomotive whole. It's the latest setback in an audacious plan to tunnel beneath the river and bring trains into Manhattan. The Pennsylvania Railroad is the largest corporation in the world, but the goopy riverbed keeps fighting back. How did they finally break through? And why are these 115-year-old tunnels still the most critical infrastructure in America?

Special thanks to our guests: Polly Desjarlais, content and research manager at the New York Transit Museum; Jill Jonnes, author of Conquering Gotham: A Gilded Age Epic: The Construction of Penn Station and Its Tunnels; and Andy Sparberg, former LIRR manager, transit historian, and author of From a Nickel to a Token: The Journey from Board of Transportation to MTA.