The mining industry was one of the industries that developed the most with the expansion of the western territory. The search and extraction of gold gained great strength, this period was known as gold rush to a period of hasty migration and mass workers to more rustic areas, in which there had been a spectacular discovery of gold commercials. It usually refers to the one that occurred in California in 1848. It ended in 1960.
Throughout the nineteenth century the population of the western United States grew extraordinarily because of two factors: The constant arrival of European immigrants, mostly young, coming mainly from Britain, Ireland and Germany, the high birth rate .
The United States experienced strong economic growth, especially since the 1830s. This was due to: The availability of an abundant and young labor force. the development of technical innovations, especially in the textile industry and in steam navigation, the early application of the methods of division of labor and chain production in factories.
The textile industry, benefited by the improvement of the machines, promoted industrialization at first. Later, the expansion of the railway lines gave rise to a powerful steel industry that soon became the engine of economic development.