The speed at which the United States grew during the 19th Century astonished observers in the older nations. The changes were not only in size but in kind. Farmers and villages gave way to factories and cities. Thomas Jefferson’s earlier America, where “every one may have land to labor for himself, if he chooses,” disappeared. In its place by 1900 was a nation where fewer than four workers in ten were in agriculture; four families in ten lived in an urban area; and industry produced 31.9 per cent of the world’s coal, 34.1 percent of its iron and 36.7 percent of its steel. With a population larger than that of any European country except Russia and with exports greater than the United Kingdom’s, the United States was already the foremost industrial country of the world.
Changes of this magnitude inevitably strained the social structure underlying this industrial might. Most conspicuously, the businessman became the most important figure in society. The merchant, the factor, the banker had of course been important earlier. They had, however, wielded less power, touch fewer lives. The millionaires, and multimillionaires of 1900 paid the wages of millions of workers and, indirectly as buyers, shippers or processors of timber, farm products and livestock, affected the livelihoods of most families in the country. No income taxes subtracted from their enormous fortunes. No regulatory agencies interfered with the methods of doing business. They were answerable only to their consciences, and these consciences were comfortably insulated; for even from the pulpit they heard social Darwinist slogans affirming that life was inherently a struggle, that the fit merited riches and that the unfit deserved exploitation and poverty.
To describe the America of this time, one has to begin by identifying the rich and by describing the magnitude of their power. One must then go on to tell of other Americans, above all of those in the middle class, who launched a battle to humble the plutocracy, to uplift the poor and to make America a country of equality, opportunity and freedom. For it was these struggles and their forward-looking resolutions that made the years 1901-1917 the Progressive Era. (E.R May, 1964)
For a better understanding of the History of the Progressive Movement.