What caused the great economic inequality between the rich and poor during the Progressive Era?

During the 1750s, before the industrial revolution, why did most people see little of the world?

The idea of manifest destiny simply stated it was america's destiny to expand from the atlantic ocean to the pacific. the word "destiny" implies an idea that it was within our rights as a nation to expand. in a paragraph of 125+ words, explain what could be wrong with that idea.

The united states economy makes up how much of the worlds economy