High Quality Content by WIKIPEDIA articles! The U.S. state of Nebraska first required its residents to register their motor vehicles and display license plates in 1915. All plates were made of steel until 1947 when aluminum plates were introduced. Nebraska established a county-coding system for its passenger plates in 1922. These one- or two-digit prefixes were assigned based on the number of registered vehicles per county in that year. In 2002, the Nebraska Legislature discontinued the 1922 system for Douglas, Lancaster, and Sarpy Counties. In 2011, upon introduction of the new plates at that time, Dakota County will discontinue the 1922 system as well.