Bethel Island, CA has a population of 2,199 and is the 10,488th largest city in the United States. The population density is 419 per sq mi which is 80% higher than the California average and 362% higher than the national average. The median age in Bethel Island is 56 which is approximately 56% higher than the California average of 36. In Bethel Island, 66% of the population over 15 years of age are married, 91% speak English and 8% speak Spanish. 68% of Bethel Island residents were born in California, 27% were born out of state, 2% were born outside of the United States and 3% were foreign born.