Walnut Creek, CA has a population of 67,568 and is the 546th largest city in the United States. The population density is 3,420 per sq mi which is 1372% higher than the California average and 3675% higher than the national average. The median age in Walnut Creek is 49 which is approximately 35% higher than the California average of 36. In Walnut Creek, 61% of the population over 15 years of age are married, 75% speak English and 5% speak Spanish. 47% of Walnut Creek residents were born in California, 28% were born out of state, 2% were born outside of the United States and 22% were foreign born.