S1, E106: Armed with his Appleton's Guide, Michael Portillo reaches a milestone on his American journey: the boundary between the northern and southern states, known as the Mason-Dixon line. He discovers the origins of what became for black Americans the border between slavery and freedom, in an 18th century English dispute over land. On the heritage Wilmington and Western Railroad, Michael meets Phoebe Snow, created to reassure passengers that clean burning coal wouldn't make their clothes dirty.