Charter Oak, CA has a population of 9,401 and is the 4,126th largest city in the United States. The population density is 10,132 per sq mi which is 4260% higher than the California average and 11084% higher than the national average. The median age in Charter Oak is 34 which is approximately 6% lower than the California average of 36. In Charter Oak, 51% of the population over 15 years of age are married, 59% speak English and 28% speak Spanish. 66% of Charter Oak residents were born in California, 11% were born out of state, 1% were born outside of the United States and 21% were foreign born.