During the 1840s and 1850s, Americans experienced a profound economic transformation. Since 1800, the total output of the U.S. economy had multiplied twelvefold. Four fundamental changes in American society fueled this remarkable economic growth. First, millions of Americans moved from farms to towns and cities, Abraham Lincoln among them. Second, factory workers (primarily in towns and cities) increased to about 20 percent of the labor force by 1860. Third, a shift from water power to steam as a source of energy raised productivity, especially in factories and transportation. Railroads in particular harnessed steam power, speeding transport and cutting costs. Fourth, agricultural productivity nearly doubled during Lincoln’s lifetime, spurring the nation’s economic growth more than any other factor.

Historians often refer to this cascade of changes as an industrial revolution. However, these changes did not cause an abrupt discontinuity in America’s economy or society, which remained overwhelmingly agricultural. Old methods of production continued alongside the new. The changes in the American economy during the 1840s and 1850s might better be termed “industrial evolution.”