
Six-digit all-numeric serials were introduced in 1916, followed in 1925 by seven-digit serials. When 99999 was reached in 19, serials with one letter and four digits were issued.

Serials were all-numeric and originally ran to five digits. The legislation authorizing the state issuance of license plates also provided for the registration and plating of motorcycles, and issued special licenses and plates to mechanics and chauffeurs. Front and rear plates were required each year, along with an aluminum dashboard disc whose number matched the serial on the plate. The state began to issue license plates in 1911. Registrants were issued a numbered aluminum disc to place on their dashboard, but they had to provide their own license plates. Automobile owners in Illinois were first required to register their vehicles with the Secretary of State's office in 1907, paying a one-time registration fee of $2.
