The document discusses the significance and impacts of the expansion of railroads in the United States in the 19th century. It led to the standardization of time zones across disconnected towns and helped industries ship goods to new markets. It also increased immigration and migration to the West. However, it presented hazardous working conditions for railroad workers. It then outlines several events that helped establish the federal government's right to regulate private businesses like railroads to protect the public interest, such as corruption scandals, state regulation laws, and the Interstate Commerce Act of 1887.