333 U.S. 364 (1948)
United States v. United States Gypsum Co.
The issue was whether the concerted actions of the gypsum companies constituted a violation of the Sherman Antitrust Act by intentionally restraining trade and maintaining artificially fixed prices.
Under the Sherman Act, any contract, combination, or conspiracy in restraint of trade or commerce among the several states is declared illegal. The per se illegality of certain practices, like price-fixing agreements, is affirmed if the defendant's actions disrupt the competitive balance of the marketplace without an overarching legitimate business justification.
The Supreme Court held that the actions of the gypsum companies represented an unlawful restraint of trade in violation of the Sherman Act, as their coordination on pricing was deemed anticompetitive and not justified by any legitimate business necessities.
This case is significant as it clarified the application of the Sherman Act to price-fixing activities, affirming that certain business conspiracies are inherently anticompetitive and do not require detailed examination of their market effects to be deemed illegal. Its analysis of cooperative behavior and competition laid foundational principles for subsequent antitrust cases. For law students, understanding this case is crucial to grasping not only the specifics of price-fixing but also the broader principles guiding antitrust enforcement.