The United States became a leading industrial power in the nineteenth century. This happened because of the four fundamental changes that took place in American society and encouraged the economic growth. First fundamental change was shift of millions of Americans from farm to towns and cities. Second fundamental change was shifting from water to steam as a source of energy and this led to increase in productivity. The construction of the railroads was the third fundamental change. The railroads harnessed the steam power and the transportation became faster and also the costs were reduced.