Question

Which business practice did Rockefeller repeatedly use that helped him succeed in building his oil monopoly

Answer 1

In all his businesses, Rockefeller made a profit and used it to expand or buy other businesses.

John Davison Rockefeller Sr was regarded as the richest person of all time in the United States, and the wealthiest person in modern history. He became richer with the rise of importance of oil and kerosene and he ended up controlling 90% of the oil market in the United States. He set up the Standard Oil Company. Furthermore, he became an influencer over the railroad industry with the transportation of his oil across the U.S.

Answer 2

He monopolized oil so that no one else could compete with his businesses. There was so controversial, so called, "cheating" involved but it doesn't really matter, he gave most of his wealth to charity.