Pima County, located in southern Arizona, was formed in 1864 by an act of the First Legislative Session of the Territory of Arizona. The county seat is Tucson, Arizona.

The collection contains financial accounts, petitions, bonds, reports, leases, deeds, abstracts of titles, tax lists, bids, and correspondence related to Pima County operations. Chiefly includes records of the Board of Supervisors, such as letterpress copies of correspondence, petitions for appointments to county office, and financial demands and warrants. Other Board records include 1879 orders to incorporate the villages of Tombstone and Arivaca, and papers related to the construction of the first and second County courthouses. Assessor records consist of correspondence and a 1900-1907 block book.

School records include financial records, correspondence, and reports. Teachers' monthly reports indicate number of students enrolled; reports for Florence, 1873, and Tres Alamos, 1874-1875, give student names. School census reports, 1874-1904, list student names, race, whether native or foreign born, and parents' names. Records of other county offices are from the Justice Court, District Court, Coroner, County Hospital, Jailer, Sheriff, Treasurer, and Election Office. A Probate Court docket dating from 1883 to 1885, and an Arizona tax list is for 1879 are also included.

Some records relate to bonds for County services such as road overseers, constables, justices of the peace, butchers, physicians, and provisions for the indigent sick and prisoners. Also present are records of the Calabasas, Tucson, and Northwestern Railroad Co., from 1885 to 1886 and 1892; also the Tucson and Gulf of California Railroad, 1882-1884.