Clearlake, CA has a population of 15,070 and is the 2,821st largest city in the United States. The population density is 1,488 per sq mi which is 540% higher than the California average and 1542% higher than the national average. The median age in Clearlake is 40 which is approximately 11% higher than the California average of 36. In Clearlake, 43% of the population over 15 years of age are married, 80% speak English and 19% speak Spanish. 72% of Clearlake residents were born in California, 19% were born out of state, 0% were born outside of the United States and 9% were foreign born.