A statute promulgated by the State of New York (plaintiff) prohibited vehicles devoted solely to displaying advertisements, but permitted business vehicles to display signs related to their business as long as the business vehicles were not solely used for advertising. Railway Express Agency, Inc. (defendant) was engaged in a nationwide express business and operated about 1,900 trucks in New York City. It sold the space on the exterior sides of its trucks for advertising that was primarily unrelated to its business. Railway was convicted of violating the New York statute in the magistrate’s court and fined. The conviction was sustained by the Court of Special Sessions, and the court of appeals affirmed. Railway Express Agency, Inc. appealed to the United States Supreme Court on the grounds that the regulation did not bear a rational relation to a legitimate state purpose and was thus unconstitutional under the Equal Protection Clause.