John D. Rockefeller and the Standard Oil Company achieved financial success by

John D. Rockefeller and the Standard Oil Company achieved financial success by the establishment of a monopoly in the oil industry.

Explanation:

John D. Rockefeller was the person who created the Standard Oil Company. In 1865, he borrowed some money to acquire some of the businesses that belonged to his partners, as well as take control of the largest refinery in Cleveland. During the next years, his business expanded especially because he acquired new partners.

In 1870, he established the Standard Oil Company of Ohio accompanied by his brother William, Henry Flagler, as well as some other men. This industry achieved a monopoly concerning the oil industry because the company acquired rival refineries and it developed some other companies to distribute and promote its products throughout the world.

Answer: Monopoly