The Hepburn Act of 1906 strengthened the Interstate Commerce Commission, stating the government's regulatory power more definitively.

The Hepburn Act empowered the ICC to change a railroad rate to one it considered "just and reasonable," after a full hearing of a complaint. The Mann-Elkins Act placed the burden of proof on the railroads; for the first time, they would have to actively demonstrate that a rate was reasonable.

With these new powers, the ICC gained almost complete control over rail rates, and therefore much of rail competition.