Rivers, so central to the world of the nineteenth century, are now peripheral at best. Interstate highways, on the other hand, are the principal means of travel by land,

Parkways were, in general, laid through thinly populated suburbs or open countryside and were designed to carry only cars. Expressways would be laid—after World War II—through cities, and were designed to carry trucks also, to serve as arteries for the commerce as well as the pleasure of a people.