Shame on you Professor Hillbilly !
During the period to which you refer, roughly from the end of the Civil War to 1900, the US economy doubled, and doubled, and doubled. That's right, exploded eight times over within the working career span of people of that age.
And what happened to prices? Deflation - that's right, ala Great Depression - except it was great expansion instead. Consumer prices in 1900 were only half of what they had been 35 years before, even with 8 times as much wealth to go around. A little math - hmmm - 16 times as well off? There must have been at least some working people who were.
As Criss pointed out, those "robber barons" were captains of industry. Did Carnegie's steel industries bankrupt the country? Or Vanderbilt's railroads?
In fact, the US catapulted into a world power at that time, and modernized at a rate perhaps unequaled in world history.