By the late nineteenth century, businesses began to form combinations, known as trusts, which claimed a larger and larger share of the market—large enough to dictate prices, their detractors claimed.
Members of both major parties were concerned with the growth of the power of trusts and monopolies, and at the opening of the 51st Congress Sherman proposed what would become the Sherman Antitrust Act.
The bill Sherman proposed was largely derivative of a failed bill from the previous Congress written by Senator George F. Edmunds, which Sherman had amended during its consideration.
Until 1888, Sherman had shown little interest in the trust question but it was rising in the national consciousness, and Sherman now entered the fray.
The revised bill Sherman proposed was simple, stating that "[e]very contract, combination in the form of trust or otherwise, or conspiracy, in restraint of trade or commerce among the several States, or with foreign nations, is declared to be illegal".
The bill further prescribed criminal penalties for any person who monopolizes trade.
In debate, Sherman praised the effects of corporations on developing industry and railroads and asserted the right for people to form corporations, so long as they were "not in any sense a monopoly".

The bill passed the Senate by an overwhelming 52–1 vote and passed the House without dissent.
President Harrison signed the bill into law on July 2, 1890.
When Harrison signed the Act, he remarked, "John Sherman has fixed General Alger."
Sherman was the prime mover in getting the bill passed and became "by far the most articulate spokesman for antitrust in Congress".
The Act was later criticized for its simple language and lack of defined terms, but Sherman defended it, saying that it drew on common-law language and precedents.
He also denied that the Act was anti-business at all, saying that it only opposed unfair business practices.
Sherman emphasized that the Act aimed not at lawful competition, but at illegal combination.
The later analysis was more generous: "The Sherman Act was as good an antitrust law as the Congress of 1890 could have devised."
By the late nineteenth century, businesses began to form combinations, known as trusts, which claimed a larger and larger share of the market—large enough to dictate prices, their detractors claimed. Members of both major parties were concerned with the growth of the power of trusts and monopolies, and at the opening of the 51st Congress Sherman proposed what would become the Sherman Antitrust Act. The bill Sherman proposed was largely derivative of a failed bill from the previous Congress written by Senator George F. Edmunds, which Sherman had amended during its consideration. Until 1888, Sherman had shown little interest in the trust question but it was rising in the national consciousness, and Sherman now entered the fray. The revised bill Sherman proposed was simple, stating that "[e]very contract, combination in the form of trust or otherwise, or conspiracy, in restraint of trade or commerce among the several States, or with foreign nations, is declared to be illegal". The bill further prescribed criminal penalties for any person who monopolizes trade. In debate, Sherman praised the effects of corporations on developing industry and railroads and asserted the right for people to form corporations, so long as they were "not in any sense a monopoly".
The bill passed the Senate by an overwhelming 52–1 vote and passed the House without dissent. President Harrison signed the bill into law on July 2, 1890. When Harrison signed the Act, he remarked, "John Sherman has fixed General Alger." Sherman was the prime mover in getting the bill passed and became "by far the most articulate spokesman for antitrust in Congress". The Act was later criticized for its simple language and lack of defined terms, but Sherman defended it, saying that it drew on common-law language and precedents. He also denied that the Act was anti-business at all, saying that it only opposed unfair business practices. Sherman emphasized that the Act aimed not at lawful competition, but at illegal combination. The later analysis was more generous: "The Sherman Act was as good an antitrust law as the Congress of 1890 could have devised."
John Sherman