Fullerton, CA has a population of 139,491 and is the 191st largest city in the United States. The population density is 6,218 per sq mi which is 2576% higher than the California average and 6763% higher than the national average. The median age in Fullerton is 35 which is approximately 4% lower than the California average of 36. In Fullerton, 52% of the population over 15 years of age are married, 52% speak English and 25% speak Spanish. 53% of Fullerton residents were born in California, 14% were born out of state, 1% were born outside of the United States and 32% were foreign born.