The U.S. state of Montana first required its residents to register their motor vehicles and display license plates in 1913. As of 2024[update], plates are issued by the Montana Department of Justice through its Motor Vehicle Division. Front and rear plates are required for most classes of vehicles, while only rear plates are required for motorcycles and trailers.
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.[1] The 1956 (dated 1957) issue was the first Montana license plate that complied with these standards.
All optional plates issued from 2003 onwards use an ABC123 serial format. Since 2012, this format has also been used on the Montana Centennial replica plate (above).
Montana established a numeric county-code system for its license plates in 1934, which remains in use today (except on optional plates). With some exceptions, the order of the codes is based on the respective populations of the state's 56 counties according to the 1930 United States census.[4][5]