Question

How did John D Rockefeller horizontally integrated his monopoly in 1880

Answer 1

He created a trust that controlled 90% of the nation's oil refineries. If I remember correctly, horizontal integration is when you buy out the other businesses in the same market, while vertical integration is where you take control of everything related to your product, which is getting the oil, refining it, and distributing it, rather than selling those tasks out to third parties.