The U.S. state of Washington first required its residents to register their motor vehicles in 1905.

[2] As of 2023[update], plates are issued by the Washington State Department of Licensing.

The plates have been manufactured by incarcerated workers managed by the Washington State Department of Corrections since 1923.

They are primarily produced at the Washington State Penitentiary in Walla Walla, with some also made at the Monroe Correctional Complex in Monroe.

[3] 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.