“Between the end of the Civil War and the early 20th century, the United States underwent one of the most rapid and profound economic revolutions any country has experienced. There were numerous causes for this explosive economic growth. The country enjoyed abundant natural resources, a growing supply of labor, an expanding market for manufactured goods, and the availability of capital for investment. By 1913, the United States produced one-third of the world’s industrial output—more than the total of Great Britain, France, and Germany combined.”