The Second Industrial Revolution followed and expanded upon the first. Advancements in transportation (rail network), communication (the telegraph), entrepreneurs (such as Andrew Carnegie, nicknamed "Captains of Industry" and "Robber Barons"), technology (Bessemer process, removing impurities from molten steel), labor (labor force growing due to the influx of immigrants and newly-freed African Americans), government (encouraged expansion, free trade, and passed tariffs), and natural resources (due to settlement in the west).