He was appointed Indian agent for Nothern California and this position continued for the work of the government of Mexico. He was among the eight Californios who were appointed to serve California constitutional convention.
He was elected subsequently to the first senate state. The conquest of California by united states was ultimately disastrous for other Californios and for Vallejo. Californios were left automated minority by the flood of immigrants into California. Vallejo was the leading member of Mexican California's population.
