The microfilm contains published volumes produced annually (except during World War II) by the Motor Vehicle Dept. Though the volumes generally were filmed chronologically, they had varying internal arrangements over the years and the license plates were issued and grouped in varying categories. The most continuous categories are automobiles (present for 1912-1959), trucks (1918-1946), motorcycles (1912-1944), and plates issued to dealers (1912-1947). Other categories include:
- Farm trucks (1935-1947)
- Insert trucks (1941-1947)
- trucks registered quarterly instead of yearly
- In transit (1929-1947)
- plates for trucks used to haul new cars to dealers
- Motorcycle dealers (1915-1947)
- Municipal motorcycles (1925-1947)
- publicly owned motorcycles
- Municipals (1925-1947)
- before 1941 all non-cycle publicly owned vehicles; after 1941, all non-cycle publicly owned vehicles except police cars
- Municipal police cars (1941-1947)
- Buses (1926-1947)
- Intercity buses (1927-1940)
- after 1940, they were listed with the rest of the buses
- School buses (1946-1947)
- Trailers (1928-1947)
- Cabin trailers (1940-1947)
- Insert trailers (1941-1947)
- trailers registered quarterly instead of yearly
- Limited trailers (1940-1947)
- trailers with a reduced registration fee for use within a 2-mile radius of their residence
- Duplicates (1925-1947)
- identical license plates which were also numbered consecutively for record keeping
The volumes on the film are most often arranged internally by category of vehicle registration and thereunder numerically by license plate number. In some places, however, they are arranged in monthly volumes, and thereunder numerically. These places are denoted on the following list with an asterisk (*). There are also a few places where the plates are arranged by county, and thereunder numerically. These are denoted with a pound sign (#). For several years after 1931, trucks, trailers, and their corrections are arranged numerically by fiscal year (July 1- June 30), whereas automobiles, buses, and motorcycles are arranged numerically by calendar year (January 1 - December 30). On the following list, fiscal issues always will precede calendar issues for any given year. For example, in the 1931 reels, the fiscal listings of trucks precede the calendar listing of autos.
There are several volumes for each year and usually a portion of each category appears in each volume. (Volumes were actually issued in sections labelled supplements; these numbered supplements have not been indicated on the contents list portion of this register.) At the end of each year's listings, the Motor Vehicle Dept. recorded all the vehicle sales changes that occurred during the year; these are designated Transfers and Corrections and cover all of the categories for that year.
Beginning in 1924, license plate numbers were assigned with a letter prefix and thereafter grouped in the volumes within that prefix; this practice ceased however in 1934 for the automobile and motorcycle categories only, which returned to a straight numerical listing. For all of the years after 1941, trucks and insert trucks license numbers may contain a suffix such as CX1, PX1, C1, or P1. Since these do not affect the numerical ordering of the classifications, they have not been indicated in the following list. In 1946, automobiles began being arranged within groupings with a number prefix, and in 1952, letter prefixes for autos were adopted once more. Of the other categories, some used letter prefixes and some did not; the microfilm reel list which follows indicates the letter prefix when it was used in arranging the records.
With the onset of World War II in 1941, steel was in short supply. Instead of reissuing plates annually, the Motor Vehicle Dept. merely recorded changes in registrations during each year between 1941 and 1945. In 1946, the Department resumed publication of a comprehensive list of plates issued.
Exceptions to the chronological order occur with records for 1912 which are found in Volume 1, Volume 2, and Volume 4 with 1913 records in Volume 3 and also in Volume 2. Volume 575 found at the end of Reel 257 contains miscellaneous records from the years 1926-1933 and 1938-1945.
