On the Move.

A traveler heading west over the National Road in 1817 noted the continuous stream of "family groups behind and before us" and concluded that "old America seems to be breaking up" and moving out to settle the frontier. Census statistics bear out his observation. By 1840 fully one-third of the nation's thirteen million souls lived between the Appalachians and the Mississippi, an area that prior to 1812 supported a substantial Indian population but only a few hundred thousand Anglo-Americans. American military success in the War of 1812 led to the expulsion of the Indians from their homelands and started a mass exodus from the East. At the same time the United States experienced a boom in population, especially in the port cities of New York, Baltimore, Philadelphia, and New Orleans.

Market Access.

Such rapid expansion, however, strained the crude communications and transportation networks of the young republic. Western farmers...