Final answer:
Rockefeller's use of horizontal integration allowed him to control the petroleum industry.
While his methods would later be deemed unfair, there were no laws in place at the time making his actions illegal.
Step-by-step explanation:
Rockefeller's use of horizontal integration was an incredibly effective business tool at the time. Horizontal integration is where a business acquires or merges with its competitors in the same industry at the same point in the supply chain. This allowed Rockefeller to gain a monopoly over the petroleum industry, thereby controlling price and quality without competition.
As for the legality of his tactics, this was a grey area at the time. Many of his methods were later categorized as unfair business practices under antitrust laws. However, these laws were not in place at the time Rockefeller was building his empire, so technically, his actions were legal then.
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