This is the 1904 legal case in which the supreme court ruled that the company in question had formed an illegal monopoly in violation of the sherman antitrust act.

The correct answer is the case of Northern Securities Co. v. United States

In this case, a company was formed that basically monopolized the entire railroad business in the United States by managing to procure all three of the major companies that dealt with railroads. The supreme court managed to ban this and ordered the company to dissolve because it violated the Sherman antitrust act.