California voter registration began in 1867, the state legislature required each county to record voter information on the local level. The registers contained the voter's name, age, occupation, birthplace, when and where the granting of U.S. citizenship occurred and the court where that took place. "Great Register" is simply the California name for voter registration records. The pages in the book are arranged alphabetically with each new registration appearing under the previous one.

The 1896 Great Register was the first to include detailed physical descriptions: height, complexion, eye color, hair color as well as visible marks, scars, tattoos, physical deformities. By 1910, no physical descriptions other than height were included. Women first start showing up in 1912, after California passed a state and local suffrage bill. By 1914, age was no longer included in the voter registrations, but specific street addresses began appearing, as well as gender. The comments column in the registration books can be very useful. They may include the date when the voter first arrived from another county where they were previously registered; when they left the county and for where; or when they died.