The following is from a work-in-progress called The Town I Live In: a History of Fullerton. The source of this information is an excellent little book by local historian Virginia Carpenter called Ranchos of Orange County (2003).
Before the town of Fullerton was founded in 1887, the land had passed through a few notable owners. For thousands of years prior to Spanish conquest of the region in the late 1700s, the land that would come to be known as Fullerton was inhabited by Native Americans, particularly the Kizh tribe. Then, in 1769, Spain began to colonize the region, beginning with the famous expedition of our local conquistador Gaspar de Portola.
In those early days of Spanish California, settlements were divided into three types: presidios (basically military forts), missions (many of which were founded by the famous Father Junipero Serra), and pueblos (towns). There were three original pueblos: Los Angeles, San Diego, and Branciforte (now Santa Cruz). Soon, however, a new type of settlement would come to dominate the landscape: the rancho.
In 1784, General Pedro Fages (governor of Spanish California) received petitions from three soldiers, requesting large land grants in exchange for services they had rendered to the government. The largest of these land grants went to Jose Manuel Perez Nieto. He got 162,000 acres of land for cattle ranching. The Los Nietos Rancho included large portions of what would become Orange County, including Fullerton.
After Nieto's death in 1804, his vast rancho was divided between his four surviving children. The family was able to hold onto most of their lands throughout the war for Mexican Independence, which transferred control of California from Spain to the newly-independent Mexico. In 1834, a soldier named Juan Pacifico Ontiveros petitioned the Mexican government for a land grant of his own. In those early days, people who'd served the government could petition for land. Ontiveros was granted a 37,000 acre rancho that was originally a part of the Los Nietos Rancho. This was called Rancho San Juan Cajon de Santa Ana. It included the land that would become La Habra, Brea, Fullerton, Placentia, and Anaheim.
After the Mexican-American War, California changed from a Mexican province to a U.S. State. This change proved difficult for Spanish/Mexican rancho families, who now had to legally prove the boundaries of their large estates. Beset by political, legal, and financial problems, the Ontiveros family sold much of their Rancho San Juan Cajon de Santa Ana off in parcels: some went to the Yorba family, some to a group of German wine-makers who would eventually found the town of Anaheim, and some to a Yankee businessman named Abel Stearns. Stearns would eventually sell part of his land to George and Edward Amerige, who founded the town of Fullerton in 1887.
And so, to put Fullerton land ownership in sequential terms, it goes something like this:
1.) Native Americans (Kizh)
2.) The King of Spain (Carlos III)
3.) Jose Manuel Perez Nieto (and family)
4.) Juan Pacifico Ontiveros
5.) Abel Stearns
6.) George and Edward Amerige
7.) Lots of different people today.