Brand books were published by different state agencies over the years: Live Stock Sanitary Board of Arizona, Arizona Livestock Board, and Arizona Department of Agriculture. They contain the brands and marks on cattle, horses, sheep, hogs, and more.
The Research Library and the Archives hold slightly different Brand Book records. You can find more information about the Research Library's Brand Book holdings at this link.
For brand information prior to 1897, check with the county recorder's office.
Image Source: Livestock Sanitary Board. Territorial Brand Book, 1897. Archives and Records Management Division. Arizona State Library, Archives and Public Records. Livestock Sanitary Board. Series One Brand Books, 1897-1919. Archives and Records Management Division. Arizona State Library, Archives and Public Records.