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Trust-busting is any government activity designed to break up trusts or monopolies. Theodore Roosevelt is the U.S. president most associated with dissolving trusts. However, William Howard Taft signed twice as much trust-busting legislation during his presidency.

Trusts were large business entities that largely succeeded in controlling a market, essentially becoming a monopoly. The term became common in the late 19th century, when a system of trusts controlled much of the economy of the United States. In 1898, President William McKinley launched the "saw-busting" era when he appointed the U.S. Industrial Commission on Trusts, which interrogated Andrew Carnegie, John D. Rockefeller, Charles M. Schwab, and other industrial titans. The report of the Industrial Commission was seized upon by Theodore Roosevelt, who became known as a "Trust-Regulator," dissolving 44 trusts during his two terms as president. The "Trust Buster" name is probably more suited for Roosevelt's successor, William Howard Taft, who brought an end to 90 trusts in one term. Although Taft may have done more to control the trusts while in office, Roosevelt retains the nickname because he was the pioneer of trust-busting.

Senator John Sherman from Ohio introduced legislation, the Sherman Antitrust Act, on July 2, 1890 to prevent trusts from forming. The Clayton Antitrust Act was enacted in 1914 to remedy deficiencies in the Sherman Act.