At the dawn of the 19th century, the size of the United States doubles with the Louisiana Purchase. The Appalachians are no longer the barrier to American migration west; the Mississippi River becomes the country's central artery; and Jefferson's vision of an Empire of Liberty begins to take shape. Historian Stephen Ambrose joins Maier and Miller in examining the consequences of the Louisiana Purchase – for the North, the South, and the history of the country.

Individual enterprise merges with technological innovation to launch the Commercial Revolution – the seedbed of American industry. The program features the ideas of Adam Smith, the efforts of entrepreneurs in New England and Chicago, the Lowell Mills Experiment, and the engineering feats involved in Chicago's early transformation from marsh to metropolis.