part of the Gilded Age and Progressive Era periods between the end of the Civil War until the beginning of the Great Depression. President Theodore Roosevelt became known as the "trust-buster" for his aggressive use of United States antitrust law, through which he managed to break up such major combinations as the largest railroad and Standard Oil, the largest oil company. According to historian David Burton, "When it came to domestic political concerns, TR's bête noire was the plutocracy." In his autobiographical account of taking on monopolistic corporations as president, Roosevelt recounted ...we had come to the stage where for our people what was needed was a real democracy; and of all forms of tyranny the least attractive and the most vulgar is the tyranny of mere wealth, the tyranny of a plutocracy. The Sherman Antitrust Act had been enacted in 1890, when large industries reaching monopolistic or near-monopolistic levels of market concentration and financial capital increasingly integrating corporations and a handful of very wealthy heads of large corporations began to exert increasing influence over industry, public opinion and politics after the Civil War. Money, according to contemporary progressive and journalist Walter Weyl, was "the mortar of this edifice", with ideological differences among politicians fading and the political realm becoming "a mere branch in a still larger, integrated business. The state, which through the party formally sold favors to the large corporations, became one of their departments." In his book The Conscience of a Liberal, in a section entitled "The Politics of Plutocracy", economist Paul Krugman says plutocracy took hold because of three factors: at that time, the poorest quarter of American residents (African-Americans and non-naturalized immigrants) were ineligible to vote, the wealthy funded the campaigns of politicians they preferred, and vote buying was "feasible, easy and widespread", as were other forms of electoral fraud such as ballot-box stuffing and intimidation of the other party's voters. The U.S. instituted progressive taxation in 1913, but according to Shamus Khan, in the 1970s, elites used their increasing political power to lower their taxes, and today successfully employ what political scientist Jeffrey Winters calls "the income defense industry" to greatly reduce their taxes. In 1998, Bob Herbert of The New York Times referred to modern American plutocrats as "The Donor Class" (list of top donors) and defined the class, for the first time, as "a tiny group – just one-quarter of 1 percent