The United States v. Grinnell Corp. et al., 1965, was a landmark case in which the Supreme Court upheld an antitrust ruling against several fire and burglar alarm companies including Grinnell Corporation, American District Telegraph Company (ADT), and Holmes Electric Protective Company for monopolizing the industry. The defendants had acquired over 87% of central station alarm services across the country through mergers and acquisitions, thereby violating Section 2 of the Sherman Act that prohibits monopolization or attempts to monopolize any part of trade or commerce among states. The court rejected their argument that they were not guilty because there was still competition from local independent companies as well as other forms of protection like watchman services or direct alarms to police stations. It held that these alternatives did not provide sufficient competition since they didn't offer similar comprehensive services provided by central station companies.

In the dissenting opinion for United States v. Grinnell Corp., Justice Black argued that the majority's decision to uphold a lower court ruling against Grinnell Corporation and other defendants was incorrect because it failed to properly apply antitrust laws. He contended that these companies had not violated any antitrust laws as they did not engage in predatory practices or seek to eliminate competition, but rather grew through legitimate business means such as mergers and acquisitions. Furthermore, he believed that this case represented an overreach of judicial power into economic matters best left to Congress or administrative agencies with more expertise in market dynamics and industry trends. By penalizing successful businesses without clear evidence of anti-competitive behavior, Justice Black warned that courts could discourage innovation and growth within American industries.