"In that period of unprecedented (and largely unregulated) growth, much of the US population became quickly enslaved by a few members of an elite group, later called the robber barons (Rockefeller, Frick, JP Morgan, Vanderbilt, Carnegie, Mellon et al.)"

You ought to rethink what you define as "enslavement". As far as I am aware, neither Rockefeller, nor JP Morgan, nor Carnegie "enslaved" the US population when they helped transform the by then agrarian nation into the industrial and economic powerhouse it later became. They didn't use force, as far as I am aware, in their dealings and the wealth of their achievements certainly wasn't created at the expense of those who didn't.