"In the beginning," John Locke wrote, "all the world was America." The land was vast, verdant, and bountiful but devoid of one element: humanity. That gap has been filled for some twenty-five thousand years, by the continuous passage of travellers who have come to the American strand, crossing first by land bridge, later ocean vessel, and then aircraft, to see what the New World presented. For some, it was a place of new beginnings and fresh starts;...