The Interstate Commerce Commission (ICC) (defendant), which no longer exists, once regulated various aspects of railroad transportation. The Interstate Commerce Act (Act) authorizes the ICC to engage in rulemaking only “after hearing.” The statute does not require that such rulemaking be on the record. After proposing a tentative order establishing rates for incentive payments, the ICC determined that it would only receive comments in written form. The ICC adopted the order, which two railroad companies (plaintiffs) challenged. The plaintiffs based their challenge on two grounds: first, that the proceedings leading up to the order did not comply with §§ 556-57 of the Administrative Procedure Act (APA); and second, that they were prejudiced by the ICC’s determination to receive comments only in written form. The district court found that the APA required that the ICC meet the formal rulemaking requirements of §§ 556-57 prior to issuing any rules. The agency sought review of the decision by the United States Supreme Court.