After California's transfer from Mexico to the United States, land ownership became one of the major flash points of hostility between native Californians and new settlers. Heavy immigration combined with differences in mapping systems and uncertainty about the validity of Mexican land titles contributed to the resentment felt by both groups. Although Anglo-Americans had been coming to California while it was still governed by Mexico, its cession to the U.S. and the discovery of gold a year later increased the stream of new settlers. And, because the Treaty of Guadalupe Hidalgo guaranteed the property rights of land owners in the ceded territories, the U.S. Government had to sift through competing claims to determine their validity, a process that often took years to complete.
While under the Mexican system, any Californian desiring a land grant applied to the Governor, listing his or her name, age, country, vocation, quantity and description of the land, and a hand-drawn map, or diseño, of the boundaries and natural features of the desired land. After consulting local officials, the Governor would decide and, if he approved, issue a formal grant in writing to the applicant. This system resulted in extremely large land grants; most were for thousands -- or even tens of thousands -- of acres. Thus a small number of wealthy landowners ran ranchos that employed large numbers of people.
The United States used an entirely different system for distributing land. Under the American system, public lands were supposed to be surveyed prior to settlement. Beginning in 1785, U.S. surveyors used the rectangular survey system, based on a grid system in which the public lands were subdivided into square townships; each of which was further subdivided into 36 square sections of 640 acres (1 sq. mile) each. After surveying and subdivision, lands would be opened up to settlement and sold at auction. Most entries were fractional portions of a section -- 320 acres or less. This system was designed to encourage the development of family farms.
To iron out the confusion over land ownership in California, Congress passed "An Act to Ascertain and Settle Private Land Claims in the State of California" in 1851. This legislation established the California Land Commission, which had responsibility for adjudicating the validity of claims to Spanish and Mexican land grants. The new law placed the burden of proof on the claimant. Because it provided for appeals of the Commission's decisions to the Federal courts, titles to these claims were often tied up in litigation for years. So, added to the conflict between the existing population and the increasing stream of new immigrants looking for places to live was uncertainty about ownership of large portions of land. Because litigation over land grants lasted years (and sometimes decades), squatting became widespread and sometimes resulted in violent clashes. Additionally, many claimants could not afford the lengthy litigation and, as a result, lost their lands.