Many of these men gained their fortunes either at the expense of their factory workers or by methods that were considered unscrupulous even back then - a time when insider trading wasn't yet outlawed.
However, many of them also gave away their fortunes to build universities, hospitals, libraries, and museums that still stand to this day.
Given that the debate about morality and business practices rages on to this day, we figured it was a good opportunity to take a look at the ruthless business practices and accomplishments of 19 tycoons who built - and ruled - America.
Editor's note: This feature is inspired by an earlier version written by Gus Lubin, Michael Kelley, and Rob Wile.