The right to private property is an integral part of the US economic system. In California, the county recorders' are tasked to maintain the public records of property ownership. This helps people prove their claim to a property.
But how did we get to this system...
Property ownership in California started with the King of Spain. He claimed of all the lands they discovered in 1542. By 1769, Spanish settlers began colonizing the land we now know as California. During this time, it was still a part of Mexico.
When Mexico became independent from Spain in 1821, the number of rancheros (ownership rights to land granted by the Mexican government - often in blocks of 35 square miles each) increased before California was annexed to the United States in 1848. These rancheros kept documents of their properties either in Mexico or with the village judge or mayor. Even now, some County Recorders' offices still maintain these documents.
When the US and Mexico signed the Treaty of Guadalupe Hidalgo in 1848, the rights of Mexican citizens to hold property in California was maintained. However, the Mexican land grants process didn’t work well with the US standards for establishing ownership of property. This led to complications in the claim of properties which, occasionally, resulted in bloodshed. Thus, once verified, the United States government issued "patents" to owners.
The lands that were not issued patents were then considered as US government property. Through land grant laws, these lands became accessible to the state of California. Some of these lands were used as railroads. Some people owned them by preemption. And others used them for homesteading.