How did we get to Arizona from Pittsburgh? When Thoreau was writing, people were moving of town, the suburbs beginning, Concord an early suburb. Farmers were selling their farms. Trains were suddenly everywhere; thousands of miles of tracks laid down in the space of a decade. The west opened up via train travel, and new roads were built to get products to farther away markets. By the early nineteen hundreds, cars appeared, first as occasional touring vehicles, and then as a means of travel.
The railroad first brought tourists to Arizona, to see the ancient civilizations of America--i.e., Native Americans. As more people got more cars, train vacation became car vacations. By the end of World War II, the state roads were turned into an interstate highway system, and roads became not for occasional use but for everyday use, to connect the suburbs that Thoreau saw the beginnings of. In the 1970s and 80s, the South became a suburb of the North. At least that's how Thoreau might see it, if it were the end of the first half and Arizona just made an interception (I think) and he had just finished a beer and was starting a second. (Library of Congress photo.)