Why then should we hesitate still to assert our independence? We have indeed taken the first step, by electing our own governor, but another remains to be taken...annexation to the United States. In contemplating this consummation of our destiny, I feel nothing but pleasure, and I ask you to share it...When we join our fortunes to hers, we shall not become subjects, but fellow-citizens, possessing all the rights of the United States and choosing our own federal and local rulers. We shall have a stable government and just laws. California will grow strong and flourishing, and her people will be prosperous, happy, and free."

   Upper California was like a piece of ripe fruit ready to fall from a tree. Distant from the central government in Mexico City (which ruled in name only), the territory was populated by a fiercely independent people. Long before the war between the United States and Mexico, American settlers had flocked to Upper California. Most settled in the Sacramento River valley near a fortified trading post called Nueva Hevetia by its owner, a Swiss immigrant named Johann Sutter. His neighbors simply called the place "Sutter's Fort." In 1846, the first player in the drama which would be termed the "Conquest of California" made his appearance. Lt. Colonel John C. Frémont. Others maintain that Frémont, being an ambitious man, acted of his own accord, or perhaps was encouraged by his expansionist father-in-law, Senator Thomas Hart Benton of Missouri.

   In the spring of 1846 Frémont asked permission from Castro and moved his man to the valley of the San Joaquin. Castro agreed, then changed his mind because of rumors that Fremont was encouraging revolt.
The explorer's response was to retreat to the top of a mountain where he and his men built a fortified camp, declaring they would "fight to extremity trusting to our country to avenge our death." After a few days, Frémont and men decided to head north for Oregon.Returning to California, Frémont turned up at Sutter's Fort. Not long afterwards, the American settlers living nearby did rise up in revolt against Mexican authorities. Whether or not Frémont incited them to action is unknown.