The Industrial Revolution took off in the late 1800s due to several key factors: new inventions like the Bessemer process for steel production, growing cities and markets, abundant natural resources, and government policies that supported businesses. Railroads connected these growing cities and markets, spurring further industrialization. Some businessmen like Carnegie, Rockefeller, and Vanderbilt amassed huge fortunes and monopolies in industries like steel, oil, and railroads. Labor unions struggled against monopolistic practices and dangerous working conditions, using strikes, but often faced violent opposition from private militias and government forces. The Sherman Antitrust Act of 1890 aimed to regulate monopolies and trusts.