In the decades following the Civil War, the US enjoyed a period of immense industrial growth. The railroad system expanded rapidly from the Northern to the Midwestern parts of the country. Less than a decade after the end of the Civil War, the country had doubled its railroad mileage. The iron and steel industry attained significant growth in the post-Civil War period. This growth was promoted by the presence of cheap and fast transportation means due to the expansion of the railways. By the turn of the 20th century, the US was producing four times as much iron as Britain produced, making the country a world leader in steel production. In the decades following the Civil War, petroleum was an important product for lighting purposes, and its derivatives were used for lubricating and cleaning purposes. The global demand for petroleum promoted the growth of this industry, and the US exploited its large petroleum reserves. The developments of these industries led to increased trade leading to great economic growth in the US.
A key economic outcome of these developments was the emergency of monopolies in the various industries. Concentrations started to occur in the railroad industry, with a few companies controlling huge tracks of the country’s railroad. A few companies dominated the steel industry, while the Standard Oil Company, established by John D. Rockefeller, dominated the petroleum industry. Industrial development led to the promotion of democracy in the US. The social structure of America was changed as people moved to urban centers where employment opportunities were great. People became more involved in the political affairs of the country, and voter numbers rose. In addition to this, economic prosperity increased the political power of the US on the global scene.