There always have been upper and lower income classes in America but the only time the difference caused problems was during the Robber Baron era, which led to the Great Depression
False assumption. The "Robber Baron era" may have preceded the great depression but it did not lead to it. What exactly did is a matter of debate, but don't speak like you know, because you don't.
There is no connection between income inequality and the overall economy or the status of the less-than-rich class. Everybody in America, at all levels of income, benefits from a free society with limited government interference and equal justice, which includes equitable taxation. This is why, despite all the efforts to socialize our country, the "poor" in America are rich compared to the world and why even the poorest born have a shot at something better.