The correct answer is "The Elkin's Act".
The first continental railroads that started to operate in the second half of the 19th century were heavily subsidized by the government. This caused major public discontent, as it was alleged that it led the railroad industry to impose predatory commercial practices on its consumers. Efforts made by the National Grange of Patron's of Husbandry in 1870 in order to change this was neutralized by interests of powerful business groups that operated in the Midwest. However, this organization's efforts led the government to create the Interstate Commerce Commission (ICC) in order to regulate commons carriers.
The "Elkins Act" forbade railroads to offer rebates to large corporations and required them to publish their rates. Nevertheless, the act did not authorize the ICC to determine whether the rates were reasonable or not, making the law inefficient.
