Final answer:
The chief effect of the Sherman Antitrust Act was to empower the federal government to break up monopolies and regulate anti-competitive practices to ensure free trade. This initiated a series of legal actions against major trusts and laid the groundwork for subsequent antitrust legislation.
Step-by-step explanation:
The chief effect of the Sherman Antitrust Act, passed by Congress in 1890, was to give the federal government the power to combat anti-competitive practices, such as monopolies and trusts, which hampered free trade. The Act aimed to promote fair competition by declaring illegal all combinations in restraint of trade, including efforts to monopolize any part of commerce or trade, especially if it affected interstate commerce. This federal law led to critical legal actions against large corporations, notably in the case of Standard Oil in 1911, which was broken up into 34 independent firms.