As New Spain expanded from the Valley of Mexico, new dioceses of the Catholic Church were established to administer the spiritual conquests of the missionary padres;. As the frontier became consolidated, the old dioceses were subdivided. In 1779, southern Arizona and parts of southern New Mexico became part of the newly created Diocese of Sonora, under Bishop Antonio Reyes, who had been one of the earliest Franciscan missionaries in Pimería Alta.

Following the Mexican War of 1848 and the Gadsden Purchase of 1854, new ecclesiastical administration problems arose. A large number of Mexican and Native Americans had been added to the Catholic population of the United States. At the request of American Bishops, Pope Pius IX created the Vicariate Apostolic of New Mexico on July 19, 1850 and appointed Fr. John B. Lamy, as Vicar Apostolic with the title of Bishop of Agathonica.

In January of 1866, Bishop Lamy sent Fathers John B. Salpointe, Francis Boucard, Patrick Birmingham and a seminarian, Mr. Vincent from Santa Fe to Tucson. Father Birmingham became the first pastor of Gila City, near present day Yuma. Fathers Salpointe and Boucard established the parish of Saint Augustine in Tucson with San Xavier del Bac as their largest mission. Mr. Vincent opened a school at San Xavier and later in Tucson. Two years later, the Vicariate Apostolic of Arizona was formed with Father Salpointe as Vicar Apostolic. His Vicariate extended from Utah to Mexico, from El Paso County in Texas to Yuma. In 1897, the Diocese of Tucson was formed.

The bulk of the records in this collection are holographic sacramental registers that document baptisms, marriages, burials and confirmations of individual church members from 1863 until 1903, from parish and mission churches under the supervision of the Vicariate Apostolic of New Mexico (1850-1867), the Vicariate Apostolic of Arizona (1868-1896) and the Diocese of Tucson (1897-present). Two earlier registers from the Spanish Colonial Period document baptisms, marriages and burials from the missions of Tubac and Calabasas-Tumacacori under the administrative supervision of the Diocese of Durango (1620-1778) and the Diocese of Sonora (1779-1829). The records of the local chapters of the Rosary Society and the Society for the Propagation of the Faith associated with the Cathedral of Saint Augustine are included in Volume 11 along with a six page reminiscence written by Petra Figueroa Stevenson, a member of the Saint Augustine congregation.