By the early 1900s, the US had become the world's leading industrial nation due to its abundant natural resources, improved transportation infrastructure like railroads, a large and growing workforce, and government policies that supported industrialization through loans, subsidies and tariffs. Major industrialists like Rockefeller, Carnegie, Morgan, Ford and Vanderbilt built vast fortunes and monopolies in industries like oil, steel, railroads and automobiles. While industrialization increased overall national wealth, the lives of many factory workers were difficult, with unsafe conditions, long hours and low pay leading to major labor strikes throughout the late 19th century.