By John Ostapkovich

Philadelphia (CBS) – Railroads have been described as critical to our nation’s expansion into a world power but also played a dual role in the war that could have destroyed it.

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The Civil War is often portrayed as industrialized North versus agrarian South but William Thomas in The Iron Way: Railroads, the Civil War, and the Making of Modern America argues that the South had been using slaves to build railroads like mad in the 1850’s. During the war, that gave its army tremendous mobility until a cataclysmic campaign.

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“We think of Sherman as destroying the South’s railroads but Sherman did something else. He destroyed railroads and then he rebuilt them and ran them for the Union Army and at the end of the Civil war, the Union Army was running the largest railroad system in the world, over 2,000 miles of rail,” says Thomas.

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Thomas relates the railroad escape of slave Frederick Douglas, Baltimore to New York by train. It took 24 hours in 1838, but would have taken two weeks just a decade earlier.