①tremendous growth of the American economy(between the end of the civil war and 1900): Steam and electricity replaced human muscle,steel took the place of iron.Machines and oil were used.People and goods could move by railroads.in 1900 it became the largest producer of coal and steel in the world.内战结束到1900年间，美国经济取得了巨大发展；蒸汽和电力取代了人力，钢取代了铁。机器和石油得到了应用，客运和货运可以通过铁路进行。煤和铁以巨大产量位居世界之首。
②features in the growth of the economy:
1) there emerged a growth of industrial and financial mergers. By 1910, incorporation had become the dominant type;
2)With the development of industry and the extension of railroad network,there was a mushroom growth of cities and urbanization;
3)there was a rapid development of new technology. The automobile and radio also developed. America was on the way of becoming a nation on wheels.
2)progressivism and some of the reform efforts.
Progressivism, also known as the Progressive Movement, appeared in America at the turn of the 20th century. It demanded government regulation(规范) of the economy and social conditions –social area:to improve living conditions of the poor, to ban child labour, work hour limit for women workers,and industrial accident insurance. Political area:to reform state and city governments and economic area:to regulate big businesses.
①the Muckrakers and Progressive Movement: The Muckrakers, a group of reform-minded journalists,made investigations and exposed various dark sides of society.Progressive Movement was not an organized campaign with clearly defined goals.Rather, it was a number of diverse efforts at political,social, and economic reforms.