Vehicle registration plates of Puerto Rico

The U.S. commonwealth of Puerto Rico first required its residents to register their motor vehicles and display license plates in 1906. Only rear plates have been required since 1976.
Passenger baseplates 1930 to present.
In 1956, the United States, Canada, and Mexico came to an agreement with the American Association of Motor Vehicle Administrators, the Automobile Manufacturers Association and the National Safety Council that standardized the size for license plates for vehicles (except those for motorcycles) at in height by in width, with standardized mounting holes. The 1955 (dated 1956) issue was the first Puerto Rico license plate that complied with these standards.