While early Spanish explorers came into what is present-day Arizona in the middle 1500s, it was considerably later before settlement began. The only portion to be actually inhabited during settlement was in and around Tucson. Under the Spanish crown, the current state of Arizona was only a part of what is present-day Sonora, and the area was known as Pimeria Alta (land of the Upper Pima).

In their search for the fabled cities of gold, Spanish expeditons encountered the Hopi and Zuni, standstone villages of centuries-old, cliff-dwelling civilizations, and the more recently arrived nomadic Apache and Navajo. Governor Diego Ortiz Parilla established a fort at Tubac in 1753, and Tucson was founded in 1775. Marauding Apaches later forced the Spanish out of the area. The seat of government shifted several times in succeeding years. It was not until 1826 that a garrison would occupy the presidios at Tucson, Tubac, and Santa Cruz. The settlements were precarious because the Apaches did not concede the frontier to Mexico.

Following the Mexican War in 1848, the boundary between the United States and Mexico stood at the Gila River. In 1854 America and Mexico concluded the Gadsden Purchase, and the boundaries of the state of Arizona and Mexico became permanent. In the recent past, much attention has been directed toward preserving, making accessible, and microfilming early Spanish and Mexican records. Manuscript collections of much of the material can be found at the state library and/or state archives at Phoenix, and the Arizona Historical Society holdings at Tucson.

In the late 1800s, by the time U.S. authorities got around to authenticating private land claims, fraud cases were relatively frequent. In 1960 these private land registers were transferred to the National Archives-Southwest Region. The Pima County Recorder's Office at Tucson should be researched for Gadsden Purchase land records, which also include mission claims. All modern-era land holdings are in the respective county recorder's offices.

For more information, see these references:

• Bancroft, Hubert Howe. The History of Arizona and New Mexico, 1530–1888. San Francisco: History Publishing Co., 1889.
• Beers, Henry Putney. Spanish and Mexican Records of the American Southwest: A Bibliographical Guide to Archives and Manuscript Sources. Tucson: University of Arizona Press, 1975.