What methods did Andrew Carnegie and john Rockefeller use to consolidate their industry?

Andrew Carnegie used vertical integration to consolidate the steel industry by controlling every aspect of production, from raw materials to transportation and manufacturing. In contrast, John D. Rockefeller employed horizontal integration by buying out competitors and forming trusts to dominate the oil industry. Both leaders achieved significant economies of scale and reduced competition, allowing them to exert substantial control over their respective markets. Their strategies set the stage for modern corporate practices in America.