Hernando de Soto was a Spanish explorer and conquistador who participated in the conquests of Central America and Peru and discovered the Mississippi River.
I can't answer your second question since I know nothing about it, my apologies, but I hope that this will help answer about Hernando de Soto.
Even if, as Berlin illustrates in a companion table, 100 percent of the African Americans living in the North were free in 1860 (compared to only 6.2 percent in the South), it still is a puzzle to figure out why the majority lived below the Mason-Dixon Line.
