Final answer:
The case Northern Securities Co. v. United States concerned the legality of the Northern Securities Trust Company and its violation of antitrust laws. The U.S. Supreme Court ruled against the trust and affirmed the decision to break it up.
Step-by-step explanation:
The case Northern Securities Co. v. United States concerned the legality of the Northern Securities Trust Company, which was a trust that included powerful businessmen such as John D. Rockefeller and J. P. Morgan, and controlled many of the large midwestern railroads. In 1904, the U.S. Supreme Court ruled against the trust in a narrow five-to-four vote and affirmed the decision to break it up, stating that it violated antitrust laws. This case was significant as it demonstrated the government's efforts to regulate big business and protect competition.