The Sherman Antitrust Act (15 U.S.C. sections 1-7), passed in 1890, is the foundational federal antitrust law in the United States. Section 1 prohibits contracts, combinations, or conspiracies in restraint of trade. Section 2 prohibits monopolization — the willful acquisition or maintenance of monopoly power in a defined market through anticompetitive conduct. To win a monopolization claim, plaintiffs must prove: (1) the defendant has monopoly power in a relevant market, and (2) the defendant willfully acquired or maintained that power through anticompetitive conduct rather than through legitimate competition. The law is enforced by the DOJ, FTC, state attorneys general, and private parties. Successful plaintiffs are entitled to treble damages under the Clayton Act. The Sherman Act has been used to break up Standard Oil in 1911, AT&T in 1984, and was central to the Microsoft antitrust case in 2001.