The vague language of the Sherman Antitrust Act of 1890 provided legal loopholes that corporations used to get around the antitrust provisions of that Act. Congress passed the Clayton Antitrust Act in 1914 to clarify and strengthen the Sherman Act. The Clayton Act strengthened consumer protection and antitrust laws by prohibiting anticompetitive price discrimination, prohibiting exclusive dealing practices, expanding the ability of private parties to sue for triple damages, permitting union organizing, and prohibiting anticompetitive mergers. The Clayton Act also held corporate officials personally liable for damages resulting from violations of the Act's rulings.
Later amendments to the Act strengthened its provisions against, among other things, unfair price cutting and intercorporate stock holdings. The Act has been the basis for many important lawsuits against large corporations.
The Clayton Antitrust Act is codified at 15 U.S.C. §12 and 29 U.S.C. § §52-53.
You can find the Clayton Antitrust Act of 1914, as amended today, at Cornell University Law Schools Legal Information Institute.