Federal, state, and local governments have long distinguished between signs (such as billboards) that promote ideas, products, or services located elsewhere and those that promote or identify things located onsite. On/off-premises distinctions proliferated following the enactment of the Highway Beautification Act of 1965. Congress directed States receiving federal highway funding to regulate outdoor signs in proximity to federal highways, in part by limiting off-premises signs. “Tens of thousands of municipalities nationwide” have adopted analogous on/off-premises distinctions in their sign codes.” D regulates signs that advertise things that are not located on the same premises as the sign, as well as signs that direct people to offsite locations. These are known as off-premises signs, and they include, most notably, billboards. D’s sign code defined the term “off-premise sign” to mean “a sign advertising a business, person, activity, goods, products, or services not located on the site where the sign is installed, or that directs persons to any location, not on that site.” D prohibited the construction of any new off-premises signs, but allowed existing off-premises signs to remain as grandfathered “non-conforming signs.” An owner could not “increase the degree of the existing nonconformity,” “change the method or technology used to convey a message,” or “increase the illumination of the sign.” The code permitted the digitization of on-premises signs. Ps are outdoor-advertising companies that own billboards in D. They sought permits from D to digitize some off-premises billboards. D denied the applications. Ps filed suit in state court alleging that the code’s prohibition against digitizing off-premises signs, but not on-premises signs, violated the Free Speech Clause of the First Amendment. D removed the case to federal court. The District Court entered judgment in favor of D. It held that the challenged sign code provisions were content-neutral based on location. The court reviewed the on/off-premises distinction under the standard of intermediate scrutiny applicable to content-neutral regulations of speech. The Court of Appeals reversed. The Appeals Court held that the on/off-premises distinction required a reader to inquire “who is the speaker and what is the speaker saying,” “both hallmarks of a content-based inquiry,” the distinction was content based. It held that the fact that a government official has to read a sign’s message to determine the sign’s purpose is enough to” render a regulation content based and “subject it to strict scrutiny.” The court held that D’s justifications for the distinction could not meet that standard, rendering it unconstitutional. The Supreme Court granted certiorari.