The document discusses the expansion of industrialization in the United States during the late 1800s. Key developments included the discovery of natural resources which fueled industry, the use of tariffs to protect American industry, and technological innovations like steel production. Industries like oil, railroads, electricity, communications, and automobiles grew rapidly. Large corporations and monopolies formed, led by entrepreneurs and financed by bankers, though working conditions were often poor. Unions struggled to gain influence among the growing urban workforce.