This eventually gets to a question that is often examined by American history students: Were the industrialists of the so-called "Gilded Age" in the United States "robber barons" who built their empires through fraud, graft, and above all exploiting the labor of the working people, or were they "captains of...
industry," whose labors helped build the United States into the world's leading industrial power by the early twentieth century? The answer to this question is a matter of perspective. Rather than providing a direct answer, it seems best to provide an analysis that looks at both sides of the question and allow you to decide.
It is absolutely beyond dispute that the Gilded Age featured widespread corruption, and that many of the actions of the wealthy industrial and financial titans were no different. Railroad tycoons (the men who were first called "robber barons" in contemporary media) conspired to raise stock prices, manipulated shipping rates, siphoned money out of government coffers, and received free land grants from the federal government, as well as many states. John D. Rockefeller, head of the Standard Oil Company, built his company into an enormous trust, pushing all competitors out of business. Leaders of many other business did the same, prevailing on politicians to pass favorable legislation. They also stood firmly against any kind of workplace regulation, and often called out state militia to crush labor disputes, as Henry Clay Frick, acting on behalf of Andrew Carnegie, did at the Homestead steel works. The gross inequalities, thorough government corruption, growth of enormous corporations, and terrible work conditions that existed across the country were the result of their actions.
At the same time, the talents of these men dramatically boosted the American economy (though it became susceptible to depressions and long recessions). Railroad magnates, corrupt or not, built the infrastructure that was largely responsible for American growth. They fostered technological innovations, developed new techniques for efficiently organizing businesses, and overall, led the American emergence as a global power. Many also donated millions to charity. Andrew Carnegie promoted what he called a "gospel of wealth," in which men like himself were obliged to spend their lives, and their money, for the betterment of society. Rockefeller also gave massive amounts of money to charities and promoted the fine arts. Economic growth led to massive inequality and an oppressed working class, but it also created a growing and affluent middle class, as new jobs were created.
So having looked at both sides of this issue, you can see that there is an abundance of arguments to be made for and against the overall impact of these men.