The U.S. state of New Hampshire first required its residents to register their motor vehicles and display license plates in 1905.
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 6 inches (15 cm) in height by 12 inches (30 cm) in width, with standardized mounting holes.
In 1977, the U.S. Supreme Court ruled that vehicle owners may cover up the mottos that a state places on its license plates.
The case began in 1974 when George Maynard, a Jehovah's Witness from Claremont, New Hampshire, and his wife taped over the "Live Free or Die" motto on their plates.
Justice Burger stated, "The First Amendment protects the right of individuals to hold a point of view different from the majority and to refuse to foster, in the way New Hampshire commands, an idea they find morally objectionable.