The Columbian Exchange
Hernando de Soto (1496-1542) was a Spanish conquistador who led a disastrous expedition of conquest into the North American interior between 1539 and 1542. De Soto, who hoped to follow in the footsteps of Cortés and Pizarro, failed in his hunt for gold on the North American mainland. After leading his men on a fruitless three-year search throughout much of what now makes up the southeastern United States, De Soto died on the banks of the Mississippi River. His men fled back to Mexico.
While De Soto's journey of conquest was an unmitigated failure, it was nevertheless historically significant. During his travels, De Soto encountered a densely populated and culturally sophisticated Indian civilization in the Mississippi Valley. However, De Soto (and his men and livestock) introduced new diseases to the region that subsequently destroyed those Indian populations. By the time Europeans returned to the area again in the late seventeenth century, the Mississippi Valley appeared to be a depopulated wilderness.