Two processes that led to the development of huge corporations in the late 1800s were horizontal integration and vertical integration. Horizontal integration refers to taking over other companies in the same industry so that a company can eliminate competition and control that industry. An example of horizontal integration during this time period was John D. Rockefeller's company Standard Oil, which completely controlled the nation's oil refining industry.
Standard Oil also used the process of vertical integration, which refers to controlling industries that produce the goods and services needed to make the company's products. It refers to a company's complete control over its own supply chain. For example, Rockefeller bought timber to make barrels in which to ship oil. He also owned kilns to dry the wood and wagons to haul the wood with which barrels were made. Therefore, he controlled the processes to supply and ship his oil. In combination with buying out his competitors, controlling his supply chain helped Rockefeller gain a monopoly over oil refining. Other companies, such as Andrew Carnegie's steel company, also used vertical integration. Carnegie owned not only steel mills but also railroads on which the steel was shipped. This process helped producers cut costs and gain control over entire industries.