The U.S. state of Oklahoma first required its residents to register their motor vehicles and display license plates in 1915.

Prior to July 1, 2019, plates belonged to the car, not the owner.

[1] 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.

[2] The 1955 (dated 1956) issue was the first Oklahoma license plate that complied with these standards.

Only issuing three-letter combinations that have not yet appeared in 1994-2009 123-ABC plates.