Who utilized Vertical Integration during the second industrial revolution?

During the Second Industrial Revolution, prominent figures such as Andrew Carnegie and John D. Rockefeller utilized vertical integration to dominate their industries. Carnegie integrated steel production by controlling every aspect of the supply chain, from raw materials to transportation and manufacturing. Similarly, Rockefeller's Standard Oil managed all stages of oil production and distribution, allowing for greater efficiency and reduced costs. This strategy enabled both tycoons to achieve significant market control and profitability.