Port Costa, CA has a population of 228 and is the 23,869th largest city in the United States. The population density is 1,440 per sq mi which is 520% higher than the California average and 1489% higher than the national average. The median age in Port Costa is 44 which is approximately 21% higher than the California average of 36. In Port Costa, 32% of the population over 15 years of age are married, 92% speak English and 8% speak Spanish. 91% of Port Costa residents were born in California, 9% were born out of state, 0% were born outside of the United States and 0% were foreign born.