This book discusses the origins and evolution of the U.S. Numbered Highway System. In 1926, a nationwide automobile highway network was created for the United States. For the first time, a set of numbered roads would span the country, ensuring that any driver could find their way beyond their own town or county by following a number. This U.S. Numbered Highway System, of which the former U.S. 66 (the 'Route 66' of song and television fame) is the best known, included a geographic logic behind its route numbering system that has become embedded in countless other networks. A hundred years after its creation, this book investigates the geographical origins of the U.S. Numbered Highway System, how it evolved within a rapidly changing country, and the ways in which it helped shape the changing geography of the United States.