ABSTRACT
By the late 1850s, the 15 slave states of the South stretched from Maryland to Texas. The Mexican War and the expulsion of the Indians had opened huge new tracts for settlement, just when cotton was emerging as America's most valuable export. Thousands of white planters moved into the new territory, bringing their families and slaves with them. Even planters in the Upper South benefited from the boom by selling their extra slaves to the expanding cotton kingdom.
