The only thing that's changed today is that a lot of these workers that are fueling our prosperity are working in coal mines, sweatshops, and cotton fields somewhere in Asia.
For a Canuck you are sure up on American history and prosperity. Why don't you tell us all how well Canada is doing in the world market these days? Shhheeeessshhhh what gall!!!!
Contrary to your previous claim immigration was never unlimited. It's impossible to compare the 1800s or even 1900s to today when travel was far more difficult. The Irish and others came here mostly on ships that took forever to make it to the states but most importantly they came legally. Today they're flying in by the millions, staying illegally or just crossing the borders as if they don't exist.