This work offers an account of where and why rail lines were built in various regions and at different times across the North American continent. It tells why the United States and Canada developed distinctive forms of rail technology surprisingly different from those of Britain, where railroading originated, and explains how these developments convey with particular clarity the continent's unique historical geography. The author takes issue with the commonly held belief that a single rail technology spread from Britain to the rest of the world. Instead, he argues, two distinct traditions of railroad building and utilization developed simultaneously - beginning in Britain around 1825 and in the United States around 1830. One defining difference, Vance explains, was that the construction of rail lines in North America was contingent on a potential market rather than an existing one. But an even greater factor was geography. Because of the great length of lines and the considerable physical barriers to rail development, North American rail companies developed powerful locomotives instead of building the costly engineering works customary in England. Few American lines had extensive tunnels or bridges because the railroads followed the terrain as closely as possible. The North American system, Vance concludes, was a mirror image of the British model of weak engines and superb infrastructure. Vance also explores the railroad's singular role in defining North American space, as lines crossed so varied and undeveloped a landscape. By 1917 the North American railnet had transformed the continent and become the most comprehensive in the world - with a quarter of the world's trackage built in the United States alone, and a third in the US and Canada combined.