In 1848 the United States took possession of California. Under the Treaty of Guadalupe Hidalgo the United States was bound to honor the legitimate land claims of Mexican citizens residing in the captured territories. In Article VIII of the treaty, the following is stated, “In the said territories, property of every kind, now belonging to Mexicans not established there, shall be inviolably respected. The present owners, the heirs and all Mexicans who may hereafter acquire said property by contract shall enjoy ample as if the same belonged to citizens of the United States.“
In order to investigate and confirm titles in California, American officials acquired the provincial records of the Spanish and Mexican governments in Monterey. Those records, most of which were transferred to the U. S. Surveyor General’s Office in San Francisco, included land deeds, sketch–maps (diseños), and various other documents.
The Congress of the United States established a Board of Land Commissioners by virtue of an act entitled “An Act to Ascertain and Settle Private Land Claims in the State of California” in 1851. The Act required a board of land commissioners to review these records and adjudicate claims, and charged the Surveyor General with surveying confirmed land grants. Of the 813 grants ultimately claimed, the land commission approved only 604. The burden of proof for the land claims was placed on the individuals seeking confirmation, in some instances this fell to the people who had bought the Ranchos from the original grantees.
Once recognized, the official map of the land was recorded at the local Recorder’s office. Some of the areas covered in these patents are in present day Riverside County, which was not formed until 1893 from part of San Bernardino and San Diego Counties.