Question

How did the Carnegie’s purchase of Allegheny Steel contribute to the formation of his monopoly?

Answer 1

Horizontal integration is when a company buys out their competitors or other companies in the same field as them in order to decrease price competition, and consumers will have no choice but to purchase from Carnegie.
Therefore, by buying out his competitors, such as Allegheny Steel, Carnegie used the concept of horizontal integration to build up his monopoly of the steel industry.