Oakley, CA has a population of 38,968 and is the 1,066th largest city in the United States. The population density is 2,457 per sq mi which is 957% higher than the California average and 2611% higher than the national average. The median age in Oakley is 34 which is approximately 5% lower than the California average of 36. In Oakley, 56% of the population over 15 years of age are married, 68% speak English and 24% speak Spanish. 67% of Oakley residents were born in California, 13% were born out of state, 1% were born outside of the United States and 19% were foreign born.