This document discusses the rise of big business in the late 19th century United States. It describes how industrialists like Andrew Carnegie in steel and John D. Rockefeller in oil amassed huge fortunes by integrating their companies both vertically and horizontally to dominate their industries. Their success contributed to the ideas of social Darwinism and that government should not regulate business, though some viewed these businessmen critically as "robber barons." It also outlines the formation of labor unions to advocate for workers' rights and better pay and conditions in response to big business.