Arnold, CA has a population of 2,624 and is the 9,544th largest city in the United States. The population density is 177 per sq mi which is 24% lower than the California average and 96% higher than the national average. The median age in Arnold is 56 which is approximately 56% higher than the California average of 36. In Arnold, 64% of the population over 15 years of age are married, 97% speak English and 2% speak Spanish. 66% of Arnold residents were born in California, 27% were born out of state, 2% were born outside of the United States and 5% were foreign born.