When the war ended, Alta California was part of the newly born country of Mexico.
Californios (how the people of California were called) were not allowed to trade with other countries when they were part of Spain only with Spain. Right after independence, they began to trade with other countries, especially the United States. They would buy several different imports; and exported mainly wheat, among other things.
The new country also established a republic and a form of government, that made it easier for other forms of trades to take place since they now had certain rules in place.
