Many experiments were conducted with steam-powered vehicles on both railways and highways. In 1804 Trevithick successfully operated a steam- powered railway locomotive which utilized a toothed driving wheel. Later experiments by Stephenson and others determined that sufficient adhesion for pulling a train could be obtained by using a smooth wheel, and the steam locomotive became a reality.
Just as the development of steam locomotives depended on improvements in iron-making, so did the development of the iron rail. Iron gradually replaced stone and wood as rail material, although a few small English railways used wood or stone rails into the twentieth century. Iron rail facilitated steam-locomotive development by carrying heavier loads than could stone or wood. Although iron rails and steam locomotives were complementary, it should not be taken that one required the other. Some railways used steam locomotives on wooden rails; others used horse power on iron rails.13
The first commercial railway to use steam locomotives was the Stockton and Darlington Railway, opened in 1825.14 This British railway used steam power and edge-rails and marked "the beginning of a new age in railway development, for although at the beginning part of the line was horse- operated, part was worked by locomotives."15
Once again, though, technological progress came by evolution, not revolution. In the United States, as in Britain, steam and horse power existed side by side for many years. A report by a U.S. civil engineer to President Jackson recommended that the Charleston and Hamburg railroad be adaptable to both horse and steam power.16 The Baltimore and Ohio Railroad used both types of power and gained a niche in history by racing its steam locomotive Tom Thumb against a horsecar. Although the horse won the race, steam power soon won the railroads.