Why was Theodore Roosevelt nicknamed "trust buster"?

President Theodore Roosevelt became known as the "trust buster" in 1904 when his administration used the Sherman Anti-Trust Act to break up the Northern Securities Company. The Northern Securities Company was a monopoly that controlled the main railroad lines from Chicago to the Pacific Northwest.

The Supreme Court upheld the break up of the Northern Securities Company on the basis that the company was an illegal combination that acted in restrain of trade. Following the court ruling, Roosevelt used the Sherman Anti-Trust Act to break up other monopolies during his presidency. These actions to regulate big business raised Roosevelt's popularity, contributing to his re-election in 1904.