From 1864 to 1900, the United States experienced one of the most significant social and economic transformations in its history. The nation became among the leading industrial powers in the world. This development is often called the "Second Industrial Revolution" because its focus was on heavy industry, particularly steel, whereas the transformation that took place in the first part of the century was primarily driven by the textile industry and the transformation of crafts performed in small workshops into large-scale mass production. This trend continued, and was in fact intensified, in the second half of the century, but the most significant advances came in heavy industry. The driving force behind this new industrial development was the expansion of the railroads, which both integrated markets throughout the United States (including the West) and provided demand for coal, steel, and other materials that were essential to industrial growth. During this period, many other aspects of the American economy were characterized by mass production, including such industries as beef and tobacco. This industrial growth resulted in the rise of massive monopolies, "trusts" that were scarcely regulated by the federal government. It was also characterized by some of the greatest extremes in wealth and poverty ever seen in the United States, as a new industrial working class emerged in American cities. These people labored in factories, mills, and sweatshops under appalling conditions, and, their ranks swelled by millions of immigrants, they increasingly looked to labor unions and even more radical solutions. So the growth of heavy industry saw the United States emerge among the world's leading economic powers, but at the cost of considerable social instability.